Backups Taken to SSDs May Not be as Safe as You Think

[bgelfand]

<p>An interesting article about long term storage of data on <strong>unpowered</strong> SSD devices.</p>

<p>http://www.extremetech.com/computing/205382-ssds-can-lose-data-in-as-little-as-7-days-without-power</p>

<p>I do not know what the implications are for backup to USB flash drives.</p>

 

[JosvanEekelen]

<p>Thanks for sharing the information.<br>

USB drives differ significantly from SSDs, so this article is not relevant for USB drives. OTOH I don't know if these lose information after a certain amount of time.</p>

[PaulCoen]

<p>I wouldn't be so sanguine about any flash storage. NAND - commanly used in flash drives - is known to have poor data retention at high temperatures. EEPROMs had the same problem, and there's no indication that mRAM is going to avoid it either. And all of them suffer from wear - after a certain number of writes, you start getting failures. It increases over time.</p>

<p>Anyone doing archiving of large volumes of valuable data is likely computing checksums on individual files, copying the data to reliable storage and to LTO-6 tape, and verifying the checksum on the copies. While any user can do the data validation, LTO drives and tapes are expensive for a home user. A well-reviewed external drive is probably fine for longer-term storage, especially if you have copies on more than one drive.</p>

<p>I'm using an online backup provider - and the software also backs up to a local external drive. Saved my bacon when a malfunctioning RAM stick in the computer lead to a few image files being damaged - I was able to go back to copies from weeks earlier.</p>

 

[bgelfand]

<p>@Jos - Although there are significant differences between a flash drive and an SSD, the one thing they share in common is NAND memory.</p>

<p>@Paul - The reason for my concern, I make off-site backups to two Flash Drives and store them in my safe deposit box. Of course these are not the only backups I have, but they are my "disaster" (the house burns down type of disaster) backup. I also have backups to an internal disk (to guard against single disk failure and "tripping over my fingers") and to an external disk, which is kept switched off unless I am actually backing up, to guard against multi disk failure and viruses. Since my backups contain financial data, I do not wish to use an online backup service.</p>

<p>I am concerned that in case of disaster, the disaster is compounded by the backups being unreadable. </p>

[PaulCoen]

<p>If I were doing "off-site", I'd be doing it with external HDD drives, not flash. I've got a fairly small safety deposit box, and I can get a drive into mine. That being said, when I priced out two drives, and factored in my time to switch them back and forth every week or two, I opted to go with a cloud provider. I also picked one that allows you to pick your own encryption key, which is stored locally. Data is encrypted before it's uploaded.</p>

<p>Most backup services allow you to select what gets backed up - you could omit the financial data from the online backup if you prefer. I happen to be using Crashplan, and I could define one backup set for cloud backup, and a different (overlapping if I choose) set for a local backup-to-disk.</p>

[bgelfand]

<p>Hi Paul,</p>

<p>I considered using 2.5" HDD (built for notebook computers they can stand more shock), but I felt that Flash Drives were more robust and could standup to transportation better. HDD on the other hand would give me much more room for backups. </p>

<p>The financial data and my home inventory are my highest priority for the off site backups. I do not trust "the cloud" for that data. </p>

[marc_rochkind]

<p>@Paul: "computing checksums on individual files"<br>

<br>

Yes, very important. But the problem with every cloud backup service I've looked at is that they do blind copies. The app says the files were backed up, and you can get a listing of what was backed up, but the only way to verify that they were correctly backed up is to do a retrieval, much too time consuming for 100GB+, which is what I have.<br>

<br>

So, I ZIP the images into big archives, verify the integrity of the ZIP, and then store the files on Amazon S3 or Glacier, which does provide a checksum.</p>

[custom film holders for fl]

<p>FWIW, If you have a Samsung 840 EVO SSD, you need to manually update the Samsung software and then the firmware of your drive. For some reason the software will not update itself to ver 4.6. When you do update to 4.6, it will finally show you there is actually a firmware update. This firmware addresses (in a hacked way) a potential data loss issue on these drives.</p>

[Hector Javkin]

<p>What isn't clear to me is whether the data loss is prevented (1) merely by having the disk powered up often enough, or (2) does the data have to be read, or re-written in order to be preserved. I would guess it has to be (1), but would like to hear that from someone who knows more about hardware than I do.</p>

[pete_s.]

<p>No one says what the how long data will be kept on an USB flash drive. But I've seen figures from NAND manufacturers indicating 10 years maximum recommended.</p>

<p>Power on or off doesn't matter in that case. But if you read all data from it and then write everything back it should be refreshed.</p>

 

[PaulCoen]

<p>The data on an SSD - for the expected life of the SSD - shouldn't have to be re-written to be preserved. Just not powering the drive off for longer amounts of time and not exposing to to high heat should be enough. <br /><br />In fact, reading and re-writing to the same drive would likely (mathematically) increase the chances of a data error occurring, since the chance of an error occurring over time is at least partially a function of the amount of data written. An error can occur on read as well, which would then make the copy damaged.<br>

<br />I've seen 16-year-old SCSI-2 drives, powered off for years, power up with all their data intact. There's likely zero chance of getting away with that with an SSD. They're really convenient and really fast. But, as always, make more than one kind of backup. </p>