2026LON Part 7: Hyde Park Cnr, Buckingham Palace, Green Park, St. Paul’s, Guildhall, Wallace Collection (& More)

Posted on August 29, 2026 by lui_gough

In this final installment of my week in London earlier this year, I look at some of the other places I visited – some of which were definitely must-see places, while others are more of a “well, at least I visited.” The photos in this post are probably not quite as photogenic as in the others due to the way the photos were sorted, but they’re still my favourites from the trip for one reason or another.

Hyde Park Corner, The Green Park

Across the road from Hyde Park is Hyde Park Corner. Yes, them Brits have a knack for naming things. This “corner” seems to be the home of a number of war memorials.

The Royal Artillery Memorial seemed to have quite the number of poppy wreaths on it.

Bronze statues stand guard, as one is laid to rest. A large bronze plaque laid on the ground carries a message …

“They died with the faith that the future of all mankind would benefit by their sacrifice.” Yet it still seems humanity can never truly be “at peace.”

Wellington Arch and a road that leads to Buckingham Palace. Every time the traffic light turns green, a throng of cyclists pass by, almost as if racing one another. But it would seem that horses don’t really care and will just leave their droppings in the middle of the road. A literally shitty situation … but definitely gives me pause to think of what a city might have looked or smelled like before the motor-car was developed.

I did particularly like the bronze statue on top of the arch, which I could get closer to thanks to carrying a zoom-lens. Quite detailed …

Then, there was this thing which looked a bit like a traffic sound barrier (sorry).

Turns out this is the Australian War Memorial which was a little more interesting when looked at up close – behind the thick next is fine text which has the hometowns of soldiers. A quote from former Prime Minister Robert Menzies – “Whatever burden you are to carry, we also will shoulder that burden.”

The Duke of Wellington on his horse …

… next to the Machine Gun Corps Memorial, with a “rough sleeper” using the benches just out of shot. There was a groundskeeper, tidying up the park, but they paid them no mind.

There is a pedestrian subway system around the corner, the route depicted on a map to help pedestrians get around without needing to wait for traffic lights. At the time I visited, I didn’t see anyone walk out of the exit … so I did wonder if it was safe. I decided not to go down … instead, it’s time to head towards Buckingham Palace.

Passing through Wellington Arch, the gates are painted green and have a very ornate design. I wonder if we could even make things this ornate nowadays – in a world that’s more driven by optimisation and cost-reduction, I’m beginning to get an appreciation for the artistic aesthetic elements which have been lost as a result.

Looking down the road called Constitution Hill, the road is nicely segmented into pedestrian, cyclist and vehicles.

More memorials are to be found inside “The Green Park” (British naming strikes again) – this one is the Bomber Command Memorial.

It would seem that quite a few relatives may have left tributes – this memorial is relatively new.

One thing I did notice is that there are a lot of paths in London that are “named”. This one is “The Diana Princess of Wales Memorial Walk” – quite a mouthful, but I suppose Diana was very beloved by the people.

The park is definitely green and while the weather seems a more appropriate miserable-grey, the experience was quite tranquil. That is, except for when I got attacked by a squirrel!

There’s a reason signs like these are around (this one was from St. James’s Park, which I visited after seeing the palace). But some tourists nearby were ignoring the signs and feeding the squirrels anyway. The squirrels become less fearful of humans and are willing to climb or bite. Once the other tourists decided to stop supplying food, the squirrels made a bee-line towards me … and started climbing my leg before I shook them off and ran. Attacked by a squirrel … that definitely was not on my list …

Buckingham Palace

The mounted police – those horses look very pretty though, especially the spotted one. Nevertheless, being the royal’s residence, this is a high-security area with crowd-control fencing and plenty of police on patrol.

Green and gold … are Australian colours, no? That’s enough gold to bribe a certain president perhaps. But in all seriousness, that’s a lot of work for a gate.

But one of the gates seems to have lost its crown – it was apparently damaged and removed for repair.

Peering into the central gate and swinging my camera about, I stitched this distorted panorama.

From a distance, the building is nice and square … but look at the vast number of tourists here for a visit! This was not a changing-of-the-guards day – I deliberately chose otherwise to avoid the crowds, yet here they are! I can’t complain too loudly – I’m also part of the problem.

The Queen Victoria Memorial stands in front of the palace …

… topped by Winged Victory, a gilded bronze statue symbolizing triumph and progress.

There are also bronze statues at the corners, featuring lions.

It would seem that Queen Victoria has seen a few restorative works over the years. I guess even things in stone don’t last forever especially in a world where pollution can cause acid rain and cold weather may cause freeze-thaw cycles that can fracture and erode delicate stonework. The tone of the replacement stonework is noticeably lighter.

The monument has a fountain, but it seems the water is switched off …

… the water would have come out of this brass relief on the side presumably, with the marble having been stained over the years from mineral deposits.

From a distance, this would be the iconic shot – another unmistakably London view.

St. James’s Park & The Mall

The mall is the main road leading to the palace and St. James’s Park (rather than St. James’ Park) forms the greenery on the other side of the road.

A monument to King George VI & Queen Elizabeth The Queen Mother.

I had to laugh because the “curse of construction” has followed me here too (wherever I go on holidays alone, construction follows).

Here, a very unconvincing faded artwork masquerades as Admiralty Arch, then limited to just one lane of traffic. Walking around this was subject to a small diversion.

A few more memorials spotted along the way …

… before I ended up at the back of the King’s Life Guard (next to Whitehall) where I had the fortune of snapping these horses going out for a trot. Such a quintessentially British shot.

Around St. Paul’s Cathedral & Paternoster Square

Heading back towards St. Paul’s Cathedral, I stopped to admire these two structures to the side – St Lawrence Jewry Drinking Fountain and The National Firefighters Memorial.

Here’s another “named” walk – the “Green Link Walk”. Not as classy when it’s like a road sign, I must say.

St Paul’s from the side – its dome is quite impressive.

Turns out – right next to it is the City of London Information Centre, a tourist information resource that I didn’t end up using. They had this map which I felt compelled to examine, which highlights key attractions in yellow.

The front-side of the cathedral – complete with a school group tour in the bottom-right of the shot. Considering this was built between 1675 and 1710, that’s quite the grand design!

Walking around to the other side, is Paternoster Square.

Did someone ask for a shepherd? The square was pretty nice, but seeing St Paul’s in the background was the finishing touch.

The walkways of Paternoster Square, lining up all-so-perfectly with one of the entrances of St. Paul’s – I quite like this perspective.

There’s even an interesting fact, plastered over a vacant retail unit. But apparently, such facts are not all that interesting to the locals …

The Underground station named after the church, but this entrance seems to be surrounded by other developments now … the dome only just peeks through in the back.

Guildhall Art Gallery

I was on my way to the Guildhall Art Gallery when I came across Wax Chandlers’ Hall, belonging to Worshipful Company of Wax Chandlers, a livery company. I suppose back in the days, wax candles were a very important commodity … but technology progresses. The box on the right is a heritage police call box in sky blue.

The Guildhall Art Gallery is definitely worth a visit – free admissions with a few floors to visit, one of which has a time-limited exhibit (if I’m not mistaken). There are exhibits which feature historical views of London, through to various sculptures and artworks that once belonged to notable names in high British society. One of the artworks was as big as the wall! I definitely enjoyed visiting, but to protect the art, I won’t share images of it …

… but I will note encountering a soap dispenser that shaves soap rather than using liquid soap (Lesseau) which I haven’t encountered anywhere else. Another thing I will note is the clear donation box for the rotating exhibit – I wonder if the clear box being filled with notes of particular denominations is a psychological suggestion to passers by as to the “value” of the exhibition. As I’ve noted, other places can be quite unashamed about requesting donations – at least here, having a box is much less confrontational.

In the same area is the Guildhall itself, the Guildhall Library and St Lawrence Jewry.

The Wallace Collection

The Wallace Collection is another free museum – this one located a short walk from Bond Street tube station.

This is truly impressive collection, not only for the sheer number of articles but the co-ordination and layout of the exhibition. Across a number of well-furnished rooms, there is plenty to see – paintings to antique curios, furniture and more. I couldn’t resist putting this one shot from inside – that lovely green wall … if only my room could look like that!

There are even a couple of fountains outside. Definitely recommend a visit – the day I was there, someone was also doing some filming, so that did disrupt the flow a little, but it seems that this was not overly crowded thankfully.

Cavendish Square, Hanover Square, Savile Row

Out of The Wallace Collection, I was intent on walking my way to Savile Row, an upmarket street famous for bespoke men’s tailors. Along the way, I crossed a number of “squares” including Cavendish Square Gardens …

… and Hanover Square. Eventually, I arrived at the row where there were plenty of expensive brands (or it would appear) and loading zones.

It wasn’t all that much to appreciate … but then a walking tour group popped up out in front of me and managed to draw me into this building …

… where the plaque informs us that this was the site where The Beatles had “played their last live performance on the roof of this building.” Historic, perhaps for fans of The Beatles … but at least I can say I’ve been here.

The Wellcome Collection

Down near Euston is the Wellcome Collection, which is a free museum with mostly science and health-related exhibits. The name is very familiar – Henry Wellcome was the founder of the Wellcome Trust which funds research in the medical field. As a biomedical engineer myself, I found it rather nice to walk around the exhibits – looking at how COVID-19 is perceived and portrayed in art and getting a feel for the various initiatives and technologies that exist to help people with various diseases. More than a museum, the building appears to have a library and some researchers or students on-site doing research (or so it would appear). I decided not to include any images just in case – but I’d say this is worth a visit if you’re in the area already.

National Army Museum

The National Army Museum was originally not on my radar, at least, until I saw it pop up on Google Maps. Located in Chelsea, next to Royal Hospital Chelsea, I found it easiest to catch a bus and take a short walk to get here. This is another free museum … but this one I felt was quite historically significant, so I will show a couple of shots from inside.

Recognise this? It’s a piece of the Berlin Wall. In fact, there’s more than one piece in the museum. To be able to walk around such an important part of history and see it with my own eyes is an interesting emotional feeling. It’s as if it makes those images in textbooks feel “real”. In some way, I suppose it reminds us that despite the conflict that exists in the world, there is also hope …

They even had a full-size chopper hanging from the ceiling as a centrepiece. Wow. What a machine! But the things I often enjoyed while walking around were the posters – plenty of recruitment ads and propaganda posters from a time when political correctness wasn’t on the forefront of people’s minds. I had a good chuckle at some of them – but I won’t reproduce them here, lest some people be offended.

Tate Britain

While the Tate Modern is perhaps the more famous gallery, Tate Britain is another one of the “Tates” that is in London. This one had a wide range of more classical British art, divided by time period with a labyrinth of rooms. It certainly is larger inside than the outside main entrance would imply. It was a rainy day, so I had the chance to enjoy some time inside – this one appeared to be a little less crowded and is definitely worth visiting. It was a shame I didn’t quite give it enough time to enjoy it completely – spending about 1.5 hours there was not enough.

Conclusion

Given that I had just a week on my own, I think it would be fair to say that I made the most of my time in London. Looking back on the list of attractions that I had “starred” on my Google Maps, the vast majority have been ticked off. Perhaps I may not have a good reason to ever return to London – but even if I never did, I’d still be satisfied that I had seen more of London than my parents did. London does suffer a bit of overtourism, so many of the attractions in London have an admission charge which is quite steep (as demand is there). Even though I focused only on the free attractions, there were plenty of significant places to visit. Even just being there, you can see the difference in architecture, city planning, height of the buildings, legacy infrastructure and feel some of the heritage of the city. This further compounds whenever you come across the myriad of plaques and memorials, referencing dates so far in the past to be inconceivable. London is a living history and I feel like being there has given me an appreciation of just how far humanity has come … but also, perhaps some hope as to how far humanity still can go. The sun may well be setting on the British empire … but nothing lasts forever.

While this post marks the end of the series of posts about my week of visiting London on my own (and avoiding all the expensive attractions), there is still one more (technical) part to come. But before that can materialise, I’m going to have to do some data analysis first …

2026LON series

BONUS: Personal/Site Update

Hello everyone!

You might have noticed that there have been a few more posts than usual over the past few weeks – that’s because I finished up my contract and am on a short career break. In this quiet time, I took a chance to catch-up on some of the many things I’ve wanted to do and post about while also doing a lot of behind-the-scenes stuff for things which aren’t quite ready to be posted just yet. But it is very exciting (at least for me) – after all, I do love answering the questions I pose about things that probably only I (and a small handful of people) actually care about. But the more I do, the more I want to do and ironically, the less it feels like I’m getting things done. Part of the reason is that posts are getting quite a bit more involved – when I started, my posts were done in a matter of half-an-hour and may have something between 5-20 images. Nowadays, posts take the better part of a day or more with close to 100 images each. I guess this is the risk that comes with digging deeper down the rabbit-hole … so I hope you don’t mind that posts sometimes don’t come about regularly or at the same pace that they used to.

Behind-the-scenes, things haven’t gone quite so smoothly – my adventures with the Solar Sharer Offer (SSO) are now complete, but did leave me a bit short on power at first, as I dialled in the right amount of storage for various appliances (which caused some disruptions). Then, I had a 1TB external SSD fail on me (VAVA) which detects the correct device ID and size but returns cleared SMART data and zeros for all sectors, while swallowing writes but reading back all zeroes. It basically turned into a write-only memory, at the height of SSD prices too! That ended up losing me a day’s work as well, but also inspired me to take a full backup of the other VAVA unit which I use as my work scratch-disk (losing that would set me back a year) which ended up costing me the better half of a day. Aside from that, I’ve been busy job-hunting which has been a little draining, but that quest will likely soon come to an end which means that I’ll be back into full-time work (which will likely mean that time for blogging will begin to evaporate again). But the past few weeks have definitely been a little stressful, even if it is partly my own doing …

That is to say, the next couple of weeks may be a little quiet, as I have been organising a two-week trip to Singapore with my Mum – another one of those things which you do while you still can, but that did add to the workload. It’s not quite fully planned but I’m sure we can just “wing it” if we must. By the time this post goes live, I’m probably packing my bags to Singapore, getting ready for an imminent departure. I’ll be very busy running around Singapore for a bit, enjoying the new MRT line extensions and LRT vehicle replacements. During this time, comments may take a little longer to be moderated, but if I do have the time, I’ll certainly try and get a couple of short posts out on my laptop (with the Carbon60 of course), but no promises unfortunately as downtime may be rather short.

As always, I appreciate all who visit my (not-so) little corner of the internet and hope to bring more interesting stuff to the blog whenever I can. Wishing my readers all the best!

– Gough

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Tested: DVD±RW Endurance Round 2 – Part 3: DVD-RAM Comparison & A Dying Drive

Posted on August 23, 2026 by lui_gough

Now, I know DVD-RAM is not a type of DVD±RW, but hear me out – I thought it was worth including in this round-up for a few reasons. The first is that it uses a phase-change recording layer, just a different formulation, meaning they share the same recording technique. The second is that my recent acquisition of DVD-RAM2 (12x) discs, I now own the lowest-endurance DVD-RAM type, often stated at 10,000 cycles rather than the 100,000 cycles of the former types. That, combined with its high rewriting speed, would make wearing out the disc potentially feasible.

As a result, in parallel, I quietly assigned one of the drives to test the DVD-RAM2 in parallel. The set-up is basically the same, but in order to maximise speeds and replicate the way that DVD±RW discs are used, hardware defect management was disabled and the full area of the disc was simply written and read back sequentially in much the same way as an ordinary rewritable disc. Unfortunately, because of the way DVD-RAM works, quality scans are occasionally interrupted as it seems the OS accesses the disk randomly, resulting in the occasional quality scan with a gap. This test was done with the same disc that previously featured in this post, thus is not a fresh disc. But given the long claimed endurance, I figured that probably wouldn’t be a problem.

So lets see if DVD-RAM2 manages to demonstrate its superior rewritability compared to DVD±RW discs.

Attempt 1 – DVD-RAM at 12x

I started with one drive and a dream to run my tests at 12x. We already know from prior experience that 12x burns are a little finicky towards the outside diameter, but I thought I’d try it anyway. Unfortunately, the drive seems to have different ideas. It decided to randomly flip-flop between 12x and 6x burns with an increasing proportion of 6x burns as it was going on. Under this regime, 1078 cycles were completed.

Unfortunately, the first verify-error occurred at 495 cycles. This is not clearly better than DVD±RW, but it seemed to flicker on and off …

It seems that dips in the TRT always occurred in the 12x burn zone. This suggests that perhaps 12x is really pushing it too far.

It seems most likely that the verify error is related to the outer diameter where there is a error “hump” that disappears every time the disc is rewritten at 6x. This suggests to me that the elevated errors towards the outer is likely a result of limitations in the mechanical rigidity of the disc and the ability of the tracking servo to compensate for tracking, focus and tilt error.

This gave me an idea – let’s reduce the speed to 6x to match the high-speed DVD-RW format. At least, in this mode, operation will be in CLV and that would relax requirements on the disc’s rigidity. Hopefully this will preserve the higher-quality write and reduce the possibility of an early verify failure.

Attempt 2 – DVD-RAM at 6x

Now, we’ve locked it down to 6x burns. This added another 2064 cycles to the disc.

Unfortunately, the first verify error now occurred at 230 cycles, but I continued to let it run to see what would happen.

Errors in the TRT are few and far-between but now cluster around 0.5GB to 1.5GB.

Looking at the quality scan, we can see a spiky region of elevated error around 0.5 to 5GB. Initially, the errors only show up in PIEs, but by 170 cycles, it was consistently showing up in PIFs which will affect readability. The spike does sometimes reduces and comes back … this doesn’t seem to be a problem with the disc but a problem with the drive or the power supply.

I replaced the power supply, but the noticed the drive was noisier than usual. I suspect mechanical failure so I set the drive aside and try another.

Attempt 3 – DVD-RAM with a New Drive at 6x & 12x

Swapping to a new drive, I try a mixture of speeds – initially 6x, then 12x for a little before returning to 6x because of the same kind of elevated errors on the 12x zone. A total of 2,055 cycles were added to the disc, for a total of over 5000 cycles throughout this part.

The first verification error now occurred after 801 cycles. Again, this is not heads-and-shoulders above DVD±RW but is more acceptable. But considering this is exactly the same disc that failed earlier twice, being able to do another 801 cycles before failing a verify suggests the disc is just fine.

Aside from the single error at cycle 801, no verify error occurred through to cycle 2055 suggesting that it managed another 1,253 cycles with no error -which would be above the rating for DVD±RW. I did terminate the test even though the disc remained working as I think I’d done enough cycles to prove that the disc itself is surprisingly durable and I didn’t want to waste excessive amounts of energy.

The TRT is mostly stable with the cycle #801 read error seemingly being the anomaly.

The quality scan instead seems to suggest the spiky error region may have been inherited from the other drive and it takes almost 300 cycles for the spike to be pared down and the error rates to become more stable. But it still seems to come back, so maybe there’s still something happening (bad firmware strategy? power supply oscillation?). While the PIFs are stably low to the point of being even better than a lot of the best-burned recordable discs, the PIEs bounce up and down like a yo-yo, which may be somewhat representative of the recording layer response changing and perhaps the power calibration is not ideal.

A Dying Drive

It seems a foregone conclusion that the drive I was using to run the endurance test is dying. As to why? I suspect it’s a worn out spindle motor bearing – the drive got louder over time and changing the power supply and even swapping to a different computer didn’t seem to resolve it. The final check-out before the drive is laid to rest is to try and get a few ordinary burns out of it to diagnose it.

The first was some decent quality MCC-004-000 – requested burn at 16x but the drive was very noisy and simply couldn’t calibrate at 16x, falling back to 8x. There is a very large error spike and error hill … that’s not what a good burner would do. The error clumps are also very unexpected. Perhaps the laser isn’t doing great either.

I gave the drive the benefit of the best media I had on hand – the MXL RG04. This one it did burn at 16x …

The burn quality was excellent – I did also test an Sony NEC Optiarc AD-7200A on a quality scan and there’s definitely a correlation, although the middle block between 1.5GB and 3.0GB looks elevated on the AD-7200A likely because there’s some variation in beta that the NEC is sensitive to.

This seems rather conflicting – I burned another disc but the drive froze-up mid-burn and didn’t finish. It’s definitely sick.

Two different types of CD-Rs, both failed the burn although at slightly different positions. I think it’s more and more likely a worn spindle motor that results in run-out (wobble) the servo simply can’t compensate for.

Unfortunately, with these results, the drive was disassembled and disposed of, as it was no longer reliable or healthy, thus no longer useful to me. It was a foreseeable outcome from using drives to do endurance tests and a key reason why I tried to standardise on using a model of drive I could readily amass in case failures were to hit so I can swap to another one to continue the experiment. Thankfully, all other drives still seem to be in good health for now, but as to how much health they have remaining, I can’t be sure.

Conclusion

While DVD-RAM is not a DVD±RW format, they are relatives as both are phase-change based recording layers. The DVD-RAM recording layer has always been advertised as having a higher endurance than that used by the DVD±RW formats. The 12x variety of DVD-RAM is advertised with the lowest endurance of around 10,000 cycles, so I decided to use it for this test.

On the basis of first verification failure, it seems that DVD-RAM did not excel far beyond DVD±RW when tested on the basis of a direct-write with verification and hardware defect management disabled. But when we consider the longest stretch of no verify failure, we achieved 1,253 cycles when the test was aborted to save energy. In all likelihood, a longer stretch of error-free cycles is indeed possible.

However, it is worth considering that this is an uncommon way to use DVD-RAM and more closely matches DVD±RW usage. However, in spite of this, any failure appeared to be a soft failure – error spots were cleared on a rewrite and the overall error rates did not escalate consistently unlike that of DVD±RW format discs. The spikes in error rate appear to be a drive-specific anomaly – one drive being bad created consistently bad spikes, but the replacement drive which is better still did exhibit an occasional spike near 0.5GB-1GB. It might just be a specific issue with the firmware or perhaps the load causes power supply oscillations … it’s hard to know for sure.

As a result, the DVD-RAM disc that I have has completed over 5000 cycles, but the final write isn’t clearly any worse in terms of quality scan result compared to what might be seen from a fresh disc. The PIF rate is surprisingly low, to the level of being better than some of the best-burned write-once discs while the PIE rate does bounce around a little, suggesting maybe there is some wear happening. When used with hardware defect management and proper formatting, bad areas would be remapped to other areas, extending the usable lifetime of the disc. That being said, DVD+RW can also support such operation in Mount Rainer (DVD+MRW) mode, although this is not mandatory or commonly used.

With that, and the loss of one of my iHAS120-6 drives, this brings Round 2 of this endurance test to an end. But even as I post this, Round 3 is in progress. Why? Well, I’ll leave that for you to guess … but this one might take a year or even longer to complete.

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Tested: DVD±RW Endurance Round 2 – Part 2: Results & Failure Modes

Posted on August 23, 2026 by lui_gough

In the previous post, I covered the contenders that would be taking part in this second round of DVD rewriting endurance tests. In this video-heavy post, I’ll be covering the results of a total of 4285 cycles of rewriting in total, although not all are successful. After all, I left the drives to keep rewriting and only checked for the first verify failure after-the-fact – most of the time, terminating the tests either after reaching over 1000 cycles or in case of the drive throwing sustained write errors.

Results

The following sections will detail the results and examine any visually apparent failure modes. A summary of the results follow.

Fujifilm 2x DVD-RW [MCC 01RW11n9]

This disc writes stably run-after-run at its rated 2x.

The first verify error occurs at run #66.

That coincides with the first dip in the TRT. After that, there are a few good runs and then another error occurs. There are long stretches of good writes between errors.

The quality scan suggests the disc was not in good health overall – the PIFs were high throughout even initially, but the quality of the burns tends to swing wildly the more rewrites that occur.

A look under the microscope seems to show there are regions of the disc, albeit infrequently compared to some of the other failure samples, where there is a darkening of the recording layer.

These spots may indicate the alloy in the recording layer is not stable in its composition and that might be the cause of the “carpet” of PIFs. But aside from this observation, the recording layer still looks visually normal.

Imation 2x DVD-RW [JVC_VictorW7]

The disc was written at the rated 2x speed.

While this is a Japanese-made disc, it’s not performing well. Only the first write seems to be taken well. The quality degrades rapidly, throwing a verify error by the third write.

The inner-diameter seems to be the area that suffers most.

Only the first write would be considered decent. Unfortunately, after the 6th run, the drive simply would not write to the disc anymore claiming of an Illegal Medium Format.

Interestingly, this disc exhibited a failure that I’ve heard rumoured about but never experienced – the claim that the embossed section of the DVD-RW disc would somehow fail after rewriting. We can see that there is some sort of dark areas developing around the embossed data.

But to blame the DVD-RW format or the embossing for the failure would be premature. Instead, this disc is suffering some form of disc rot despite the recording layer being inorganic.

This is apparent, as even away from the embossed section, there are black spots scattered about. This is a subtle form of rot, but the precipitating cause is not known. The reflective layer does not show pinprick holes on examination with light, suggesting there may be some sort of chemical issue with the recording alloy and reflective layer interacting.

Imation 4x DVD+RW [MBIPG101-W04-000]

This disc wrote consistently at 4x.

No verification errors in 1005 cycles, the test was terminated as the disc achieved the 1000 cycle lifetime expectation.

The read speed graph was consistent throughout.

The quality scan did show some yo-yoing of the write quality especially as the disc ages, with the outer diameter seemingly suffering some slow failure that increased the error rate in that area. I feel that my previously hypothesised ageing of the PCA impacting on burn quality may be supported by such observations, as the PCA is used up in a “random” order and is what varies on a burn-to-burn basis. As a result, the laser power will vary write-by-write especially if there are defects in the media’s PCA.

Imation 4x DVD+RW [RITEK-004-048]

This 4x disc wrote consistently at 4x.

The first verification error occurred at cycle 259.

The use of TRT does not detect errors until the burn is noticeably bad.

The errors seem to be at an intermediate diameter and at the outer diameter, rather severe oscillations in burn-to-burn quality was exhibited.

Memorex 2x DVD-RW [CMCW02]

This 2x speed disc burned at 2x.

At cycle #88, the first verification failure occurred.

Once again, the TRT was not very sensitive to disc failure until very severe errors occurred.

The disc seemed to develop spiky errors which increased in density as the disc aged. This suggests some sort of material degradation, but this was not apparent on a visual inspection of the disc.

Memorex 4x DVD+RW [INFODISC-A10-001]

I did not have high hopes for this DVD+RW, but it seemed to work okay at 4x.

Surprisingly, it survived 841 cycles, which is not quite 1000 but a lot more than I expected.

There are only minor jitters in the middle of the TRT prior to the disc’s first verify failure.

For some reason, this disc had a “bad patch” in the middle of the disc, even from fresh, with a carpet level of PIFs which would not have me consider the burn as being good. But the rate of degradation was low, which is ultimately what allowed the disc to survive.

Omega 8x DVD+RW [PHILIPS-RW8-000]

This disc is a high-speed disc rated at 8x, but was already used. The drive consistently wrote with a Z-CLV 8x strategy.

A total of 398 cycles were completed prior to the first verification error.

While a TRT is not highly sensitive, it does pick up on the worsening conditions towards the end of the 6x zone at about cycle 140 onward.

The quality scan result shows the burner likely was not working well with the media, with very high errors and an obvious Z-CLV jump in error and jitter. Despite the horrible looking quality scans, the disc was still smoothly readable.

Philips 4x DVD-RW [INFOMEDIAA20]

There seems to be something unusual about this media that means that the 4x disc is detected as a 6x disc as the firmware has an entry for this MID at 6x. It seemed unwise to try writing a rewritable disc at a higher speed, based on my overspeeding experiments, so I requested a 4x burn. Instead, the drive ignored the request and ploughed on through at 6x.

The first cycle resulted in a read error, so basically it was not possible to write this disc properly.

The TRT shows the outer edge to be a major issue. This is not unexpected as this disc appeared sun damaged from the start.

The quality scan implies this disc is just impossibly-badly burned.

The final write failed part-way during the write phase. It seems the disc’s formatting is permanently damaged and the disc was murdered, but less severely compared to the Prodisc DW06 (see later in this post). I wonder if the iHAS120-6 has a firmware bug or perhaps some vulnerability where incorrectly read disc metadata could result in incorrect burning of media.

Under the microscope, there are fractal/Lichtenberg figures from the outer edge where the sun damage appears to have occurred.

This suggests to me that the disc adhesive or lacquer may have failed in some way, resulting in moisture migrating into the recording layer, causing it to fail.

Pioneer 2x DVD-RW [PVCW00V00245]

The disc burned at the rated 2x and the Mediatek chipset in this drive didn’t murder the disc right away.

The disc survived 346 cycles to the first verification failure.

The disc appears to have degraded throughout the experiment, with dips starting to appear at 110 cycles near about 400MB then later towards the outer diameters.

The initial burn quality is not bad although the peaks of the PIF are still higher than I’d like. The PIE/PIF rate increases steadily as the number of rewrites increases. The “yo-yoing” really only begins at about 110 cycles.

The failure is a form of disc rot as well, resulting in visible “clearings” in spots across the disc.

Backlighting the disc suggests that this failure is precipitated by pin-prick holes in the reflective layer. Perhaps the rewritable phase change layer interacting directly with the lacquer or adhesive results in outgassing during a write (as that causes high localised heating) and that’s “blowing” up a small pocket every time the laser crosses over.

Under the microscope, those pin-prick holes create darkened spots in the recording layer. Once the hole is large enough, it seems to “inflate” an oval around the hole. Some of these defects are in the PCA, which would likely affect the consistency of recording.

This sort of defect is scattered across the whole disc, so it’s surprising the disc even survived so long. Again, this is somewhat disappointing because this is a Japanese-made disc, but it didn’t survive very well.

At maximum zoom on my digital microscope, we can see a little more detail on the pin-prick hole. It appears black – perhaps burned by the laser. The concentric rings are likely an interference effect caused by the pitch of the spiral tracks on the disc.

Smartbuy 4x DVD-RW [Prodisc DW06]

This 4x disc wrote at the rated 4x speed.

The disc was a bit disappointing, managing 110 cycles before the first verify failure.

TRT disruptions happen around the 108 cycle mark, with increasing errors towards the outer diameter.

The disc burned very well at first, then started to get really spiky towards the end. I wonder if the spikiness is related to the disc’s construction in any way.

On the final burn that failed, the drive appears to have murdered the disc, causing the disc to have an unrecognised format. Visually examining the disc, the inner tracks appear to be written in such a way to be unusually bright compared to the rest of the disc. It seems the wrong power has been used and may have damaged the recording layer permanently.

A closer look at the recording layer shows there are a few very tiny dark spots.

These spots are distributed across the media but are not uniformly dense.

Interestingly, looking at the CPRM code area, it seems there is some sort of “bloom” around the written barcode. Compare this with the disc below and it is somewhat unique. It’s not likely related to the cause of failure and could be related to viewing it through a microscope, but is still an interesting observation.

Smedia 2x DVD-RW [OPTODISCW002]

The disc wrote at the rated 2x.

The disc survived 86 cycles before the first verification failure.

The TRT is stable until the very end.

The first 56 cycles seemed to show good burn quality, but then the outer diameter becomes spiky out of nowhere.

The CPRM barcode on this disc appears a lot more “regular” to me, without the blooming around the code. Compare this with the Prodisc DW06 example above.

SWTechnology 2.4x DVD+RW [OPTODISC-OP1-001]

This disc was a big problem. It’s so problematic it didn’t even deserve any images – it burned at 2.4x just fine, but then, the disc was completely unrecognisable by the drive afterwards. The first burn killed the disc and there was nothing visual about the disc that would explain why. I suspect it’s just that the disc is either of poor quality or the strategy in the drive’s firmware is completely inappropriate.

TDK 2.4x DVD+RW [RICOHJPN-W01-001]

The predecessor to my former favourite RICOHJPN-W11, this disc runs at 2.4x.

Unfortunately, even the first burn did not pass verification.

The TRT is all over the place …

… and the quality scan implies the disc is horrible.

From a wider view, it doesn’t look like there’s anything wrong with the disc. The slightly uneven herringbone pattern is very common, even amongst good discs.

Under the microscope, microscopic dark spots can be seen although there are no visible pin-prick holes through the reflective layer. It seems this is another “rotted” disc – even brand-new discs stored well may not be usable.

TDK 4x DVD+RW [PHILIPS-041-000]

The disc burned consistently at 4x.

This disc did fairly well, reaching 551 cycles before verification failed.

The TRT is clean, with only slight dips on the outer diameter towards the end.

Burn quality is excellent, until about 190 cycles when the outer diameter starts to show some signs of distress. The outer diameter error mound seems to oscillate on and off, but at about 490 cycles, it starts to grow almost monotonically and the errored area starts to increase. There seems to be no visually discernible change to the recording layer though.

Summary

The discs of this round are highlighted in light-yellow. Of all the discs, the Imation 4x DVD-RW from Moser Baer India is the stand-out, being the second disc across both rounds to meet and exceed 1000 cycles. The Memorex 4x DVD+RW from Infodisc was also a surprise, managing 841 cycles which is pretty good. I wouldn’t have expected this from a smaller manufacturer. The Imation 4x DVD+RW from Ritek was pretty average, being fairly similar to the other Ritek discs. The Pioneer 2x DVD-RW seemed to hang in there with 346 cycles, as did the used Omega 8x DVD+RW from Philips at 398 cycles. The Smartbuy-branded Prodisc DW06 was a bit poor at 110 cycles.

Unfortunately, there were plenty of “sick” discs – the SWTech 2.4x DVD+RW (OPTODISC-OP1-001), the TDK 2.4x DVD+RW (RICOHJPN-W01-001), the Philips 4x DVD-RW (INFOMEDIAA20) and the Imation 2x DVD-RW (JVC_VictorW7) which either didn’t manage a single verified burn or only a handful of burns in the latter case. The Fujifilm 2x DVD-RW (MCC 01RW11n9), Memorex 2x DVD-RW (CMCW02) and S-media 2x DVD-RW (OPTODISCW002) all didn’t make 100 cycles and may also suggest some degradation of the recording layer.

To compare between rounds, the TDK 4x DVD+RW (PHILIPS-041-000) of this run managed 551 cycles while the previous one only managed 218 cycles. This is quite the gap, although both discs come from different batches and the tests were done on separate drives. This suggests that there might be a significant difference on individual discs and drives – but a disc that does <100 cycles doesn’t seem likely to do 1000 cycles on another drive.

Conclusion

Unfortunately, many of the discs in this second round did not fare all that well, in part because it seems they have not aged well in storage. Subtle forms of disc rot were spotted that resulted in dark spots in the recording layers which increased error rates, to those which created larger cleared regions which seem to coincide with pin-prick holes in the metallisation. A failure of a DVD-RW with visible darkening of areas around the embossed region was observed, although the failure was distributed across the surface and not exclusively at the embossed area. A good number of discs were unable to complete a single successful verification, and another managed a single-digit number.

Of the tested discs, the Imation 4x DVD+RW from Moser Baer India (MBIPG101-W04-000) managed to make it to a full 1005 cycles before the test was aborted with no failures. Honourable mention goes out to the Memorex 4x DVD+RW from Infodisc (INFODISC-A10-001) which managed 841 cycles – not quite 1000 but a lot more than I’d expect from a lesser-known manufacturer. The TDK 4x DVD+RW from Philips (PHILIPS-041-000) managed 551 cycles, which was more than the 218 cycles of the same type but from a different batch in the last round. This suggests there is some potentially significant variation from disc-to-disc and drive-to-drive.

It would seem that having an inorganic recording layer (as phase change layers are metal-oxide-based) is not, in itself, sufficient to ensure long disc lifetimes. A breach of the adhesive bonding layer may allow atmospheric attack of the protective lacquer, reflective layer and recording layer. Similarly, construction defects in the form of pin-prick holes in the reflective layer may enable contamination of the recording layer by the lacquer or adhesive layer especially when super-heated by the laser. It cannot be ruled out that some recording layers may not be stable over time, so the recording characteristics may drift without visually observable defects. As a result, brand-new discs used soon after manufacturing may have exhibited better cycle characteristics than these tests have demonstrated.

This exploration answers a lot of questions I had about the rewritability of DVDs and gave me the opportunity to test even more media. But this second round of testing isn’t over … there’s a third part which is somewhat tangentially related.

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