Hi Kristian, It would be really cool if AnandTech included a section on how a reviewed SSD handles power-loss, in future SSD reviews.
I've always assumed that when a SSD reports data as written to the OS that it was safely written to non-volatile memory. Which doesn't seem to be the case.
I'm now wondering how easily a file system can become corrupted on certain SSD's, in the event of power loss. I guess this is one area that HDDs have an advantage?
Yeah, HDDs are definitely more resilient against corruption in the event of sudden power loss since data is stored magnetically rather than electrically. But against making blanket statements regarding SSDs in general, the truth is, individual design decisions play a huge role in how graceful an SSD will behave in worst case scenarios: http://www.extremetech.com/computing/169124-the-my... http://www.zdnet.com/article/how-ssd-power-faults-...
Some SSDs are more tolerant to electrical mayhem, others, not so much. Unfortunately the number of less resilient SSDs outnumber the sturdier ones, but time may change that.
That is an interesting paper, thanks for sharing. Given it was published in 2013, I wonder if there has been any significant improvement since then.
The last paragraph of the conclusion is pretty scary: "Because we do not know how to build durable systems that can withstand all of these kinds of failures, we recommend system builders either not use SSDs for important information that needs to be durable or that they test their actual SSD models carefully under actual power failures beforehand. Failure to do so risks massive data loss"
I hope SSD manufacturers really take this on-board. SATA SSDs are certainly fast enough nowadays, maybe they can spend some more resources on improving reliability, rather than performance.
However the test was in one respect unrealistic - the power feed was cut immediately. In the event of power failure to a PC the voltage rails drop over a period of several milliseconds which would allow the controller on a SSD to terminate operations more gracefully. This would probably not help with the serialization errors but should help with the corruption errors (including mapping table corruption). Note also in a PC the CPU will normally be halted (by loss of the POWER GOOD signal) before the power feed to the SSD drops below its tolerance so the interface should be idle before the point where the SSD shuts down.
They also miss that a lot of people like myself do daily backups to an external or internal HDD (spinning drive) that is fault tolerant. Though, some people have been posting that drives with UEFI and GPT have a problem with restoration from backups using some programs. The programs in question APPEAR to backup the data correctly but in reality? They don't so when you try to restore? You cannot and lose all your data.
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Vanburen - Monday, January 12, 2015 - link
Hi Kristian, It would be really cool if AnandTech included a section on how a reviewed SSD handles power-loss, in future SSD reviews.I've always assumed that when a SSD reports data as written to the OS that it was safely written to non-volatile memory. Which doesn't seem to be the case.
I'm now wondering how easily a file system can become corrupted on certain SSD's, in the event of power loss. I guess this is one area that HDDs have an advantage?
merikafyeah - Monday, January 12, 2015 - link
Yeah, HDDs are definitely more resilient against corruption in the event of sudden power loss since data is stored magnetically rather than electrically. But against making blanket statements regarding SSDs in general, the truth is, individual design decisions play a huge role in how graceful an SSD will behave in worst case scenarios:http://www.extremetech.com/computing/169124-the-my...
http://www.zdnet.com/article/how-ssd-power-faults-...
Some SSDs are more tolerant to electrical mayhem, others, not so much. Unfortunately the number of less resilient SSDs outnumber the sturdier ones, but time may change that.
Jeffrey Bosboom - Monday, January 12, 2015 - link
Here's a paper from 2013 describing various SSD power loss failure modes observed in actual testing: https://www.usenix.org/system/files/conference/fas...Vanburen - Monday, January 12, 2015 - link
That is an interesting paper, thanks for sharing. Given it was published in 2013, I wonder if there has been any significant improvement since then.The last paragraph of the conclusion is pretty scary:
"Because we do not know how to build durable systems that can withstand all of these kinds of failures, we recommend system builders either not use SSDs for important information that needs to be durable or that they test their actual SSD models carefully under actual power failures beforehand. Failure to do so risks massive data loss"
I hope SSD manufacturers really take this on-board. SATA SSDs are certainly fast enough nowadays, maybe they can spend some more resources on improving reliability, rather than performance.
Duncan Macdonald - Monday, January 12, 2015 - link
However the test was in one respect unrealistic - the power feed was cut immediately. In the event of power failure to a PC the voltage rails drop over a period of several milliseconds which would allow the controller on a SSD to terminate operations more gracefully. This would probably not help with the serialization errors but should help with the corruption errors (including mapping table corruption). Note also in a PC the CPU will normally be halted (by loss of the POWER GOOD signal) before the power feed to the SSD drops below its tolerance so the interface should be idle before the point where the SSD shuts down.Lerianis - Wednesday, January 14, 2015 - link
They also miss that a lot of people like myself do daily backups to an external or internal HDD (spinning drive) that is fault tolerant.Though, some people have been posting that drives with UEFI and GPT have a problem with restoration from backups using some programs.
The programs in question APPEAR to backup the data correctly but in reality? They don't so when you try to restore? You cannot and lose all your data.
Impulses - Monday, January 12, 2015 - link
Use a UPS?Lerianis - Wednesday, January 14, 2015 - link
Best suggestion if you have an SSD is to only use it if you have a battery-backup.XmppTextingBloodsport - Saturday, March 19, 2016 - link
Who does not protect their electronics with true sine wave double conversion UPS?!!?