Memory cards - XQD thoughts

[jeremyrh]

Some thoughts and questions motivated by the "one card slot" issue (so please move this topic if appropriate!) and the necessity of buying XQD cards for the Nikon mirrorless bodies.

Buying new cards is an expensive business, so good to get it right. At present the choice seems to be Sony M series or Sony G series - the latter being higher write speed and much more expensive.

Is there any difference, apart from the write speed? So, if you are shooting (relatively) slowly, is there a reason to buy the more expensive card?

The age-old question about card size - if you buy small cards, losing one loses fewer pictures, but having more cards gives you more chance of getting a defective one. To resolve the question, you'd have to know what is the common failure mode of cards?  I think for CF cards one common problem was bending pins, so you may say that failure rate is a function of how many times you put the card in the camera, and hence larger cards might be "safer".  I have no idea what is the most common failure mode for XQD (does anyone?) or even SD cards. Is it some physical problem with the card? A camera software problem that affects the proper writring of data to the card?

Thoughts welcomed from more knowledgeable readers!

[Alan Goldhammer]

https://dslrbodies.com/accessories/camera-accessories/faq-about-camera-accessorie/what-causes-card-errors.html

https://www.sansmirror.com/newsviews/the-card-failure-issue.html

Both come from Thom Hogan's site an address some of the issues you pose.

[D76]

I won't give you links to look up and read.  I will give you an opinion.  Purely opinion.  I personally wouldn't sweat the "one card" hysteria.

I went digital in 2001.  I have used cameras from the Nikon D1X to current.  In the entire time I've used storage media (cards), I've never, ever, had one fail.  I've thrown them away when they've become obsolete.  I've submerged them, accidentally, in streams and rivers, dried them out and used them.  On two occasions I destroyed the camera, but not the card.  I even had a case where I inadvertently washed one in my jeans pocket.  I dried it out and it downloaded.

I buy XQD cards because the D850 uses them.  I don't have any other reason.  I buy smaller cards and change them out as I need to.  I shoot by design and my recording is slow and deliberate for the most part.  Whatever benefit the XQD card gives me is probably not appreciated nor needed in my style of shooting.

To be honest, I've lost more film in darkroom mishaps.

[Dan Wells]

Part of Nikon's reasoning behind a single XQD slot is that XQD is reliable enough that the card is no longer the most likely failure point. Very few shutters are rated past 200,000 frames, and I suspect other mechanical parts are in the same range? XQD is basically a SSD in a small package (unlike SD, which may use less reliable flash, and definitely has mechanical packaging issues), and the lifetime of the flash memory is quite a bit longer than the shutter cycle. In a shutter life of 200,000 images  (using D850 RAW file sizes, because they're both big and well known - about 54 MB), you'd rewrite a relatively small 64 GB XQD card about 168 times. A current low-end SSD (a WD Blue - more or less picked it out of a hat) has a write endurance of 100 TB for a 250 TB drive, so about 400 times (and SSDs tend to outlast their rating a couple of times over). That suggests that, at a minimum, a 64 GB XQD is good for roughly half a million D850 (Z7 raw file sizes are probably very close) images - how many people put half a million images on one relatively small card?

While it's very hard to overwhelm an XQD card with still images, video may be more likely. I could see a possible (if unlikely) workflow where a busy production shop wrote a card fully every day (weekends included) for a year. That is getting close to running into low-end SSD lifespans. I am almost sure Red SSD mags use higher-end enterprise class SSDs for that reason, which have lifespans of thousands of full-drive writes.

[JaapD]

I think the card’s reliability has never been the main problem. It’s the interface (electrical contacts). The XQD cards don’t solve this.

Regards,
Jaap.

[shadowblade]

Even if SD cards failed at five times the rate of XQD cards, I'd still take two SD cards over one XQD card.

Why? Because, in order to lose your data, it wouldn't just be a matter of having both cards fail at some stage. Rather, both cards would have to fail at the same time, which is a far less likely prospect than that of a single XQD card failing. If they didn't fail at the same time, you'd just find out on the next frame you shot - when the camera writes to one card and not the other - and replace the cards, backing up the good one. Even if the camera didn't do that, at very worst, they'd have to both fail within the same 1000-2000 shots you fit onto an SD card, before you put them into a reader and realise one of them isn't working.

A shutter failure, or other camera failure, isn't comparable. When that happens, you realise the instant it happens and can change to a backup body. You also don't lose the photos you've already taken - as long as you have a backup body (and you should, on any important shoot or long shooting trip) you can keep shooting as if nothing happened.

[jeremyrh]

I think the card’s reliability has never been the main problem. It’s the interface (electrical contacts). The XQD cards don’t solve this.

Regards,
Jaap.

Indeed. But would it be an argument in favour of "big cards" vs "small cards" ?

[D Fuller]

Even if SD cards failed at five times the rate of XQD cards, I'd still take two SD cards over one XQD card.

Why? Because, in order to lose your data, it wouldn't just be a matter of having both cards fail at some stage. Rather, both cards would have to fail at the same time, which is a far less likely prospect than that of a single XQD card failing. If they didn't fail at the same time, you'd just find out on the next frame you shot - when the camera writes to one card and not the other - and replace the cards, backing up the good one. Even if the camera didn't do that, at very worst, they'd have to both fail within the same 1000-2000 shots you fit onto an SD card, before you put them into a reader and realise one of them isn't working.

A shutter failure, or other camera failure, isn't comparable. When that happens, you realise the instant it happens and can change to a backup body. You also don't lose the photos you've already taken - as long as you have a backup body (and you should, on any important shoot or long shooting trip) you can keep shooting as if nothing happened.

Or the controller fails, taking both cards with it.

[SrMi]

To consider is that several manufacturers sell cameras where the second card slot is only in UHS-I mode. In those cases, if you use backup mode you turn your camera into a system with UHS-I cards. Imagine a manufacturer selling cameras with only UHS-I slots :-).
A second slot can be a convenience, i.e., use one slot for video, one for photos. Only those cameras that have two slots with equal speed can be considered as providing an adequate backup mechanism, IMO.
I think some people can find peace of mind by using the second card as a backup, and that is OK.

[Dan Wells]

XQD does have much-improved contacts - it doesn't solve the contact problem (only Zeiss did that, by the simple expedient of soldering half a terabyte into the camera), but it does help...

[shadowblade]

Or the controller fails, taking both cards with it.

So the logical thing is to have two separate controllers - one for each card. For proper data protection, any potential point of data loss needs to have redundancy.

Really, the best way to do it would be to have no memory cards at all, but two separate solid-state drives built into the camera, holding 512GB-2TB in duplicate, as well as an external storage device carried in the camera bag that can hold several terabytes in duplicate and can be connected to the camera by USB or WiFi to back up data and empty the camera's storage during long shoots (just as you'd replace memory cards when they're full). It would be much more reliable than any card. But, failing that, duplicate cards and controllers is the best thing we have at the moment.

[BJL]

Or the controller fails, taking both cards with it.

But hopefully not all the photos already on the cards.

I do like the idea of having some fast (PCIe/NVMe ?) internal memory, with the contents then also copied through to a removable card. That internal memory could cycle through, always holding the last so many GB of images. This might also help with buffer clearing bottlenecks, though CFexpress (and SD Express) might also solve that problem.

P. S. Anyway, XQD (meaning its heir, CFexpress) gained a lot of momentum with this month's announcements.

[Telecaster]

+1 on in-camera solid state storage plus an external SSD for longer-term storage & backup. I use a WD 2TB wifi SSD for backup in addition to a pair of traditional drives. For travel the SSD fits easily in a camera bag or my iPad's soft carrier.

-Dave-

[D Fuller]

So the logical thing is to have two separate controllers - one for each card. For proper data protection, any potential point of data loss needs to have redundancy.

Really, the best way to do it would be to have no memory cards at all, but two separate solid-state drives built into the camera, holding 512GB-2TB in duplicate, as well as an external storage device carried in the camera bag that can hold several terabytes in duplicate and can be connected to the camera by USB or WiFi to back up data and empty the camera's storage during long shoots (just as you'd replace memory cards when they're full). It would be much more reliable than any card. But, failing that, duplicate cards and controllers is the best thing we have at the moment.

I love the idea of hard-wired storage, but I think cards have their purpose as well. I’d favor a 250-500GB non-volitile write-through buffet that provided backup for the most recent data that passes through it, but allows me to take a card out to offload to whatever backup storage I want and keep on shooting.

SSDs, unless they come in some form factor I’ve not yet seen, are just too big. And are they really less suceptible to failure than C-Fast or XQD?

[BJL]

Telecaster and D Fuller,

    for all practical purposes XQD cards are a kind of small removable SSD: they use the same non-volatile flash memory with "state of the art" PCI Express interface, and their heir CFExpress also upgrades to the newer NVMe protocols. In fact they are like the new, faster kind of SSD, as opposed to (cheaper and more common) ones using the older SATA interface. In particular, the CFexpress standard allows for other form factors in the future, some using more PCIe lanes, so it seems to be aimed at becoming "the" standard for external/removable solid state storage devices, including larger, faster formats for professional video/cine cameras and such.

[Rayyan]

Any card readers for them yet? Price?

[jeremyrh]

Any card readers for them yet? Price?

Sure  The Sony one is £27 on amazon.co.uk

[DP]

XQD cards are a kind of small removable SSD: they use the same non-volatile flash memory

where did you get an idea that XQD are using any different flash memory cell technology than SD cards like Toshiba Exceria Pro ?

[BJL]

I didn’t say that: I said that the basic memory type is the same as in SSDs. AFAIK, the inherent disadvantages of SD are not due to the type of memory chips used, but mechanical vulnerability, speed, and so on.


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[Dan Wells]

I've read that SD uses a slightly different type of flash chip (shared with USB keys) from XQD (shared with SSDs)... I'm not sure exactly what the technical differences are.