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I have seen some weird issues with SSDs. I had an OCZ Vertex 2 die on me multiple times, but one thing that stood out most is that after a power cycle or comple

I have seen some weird issues with SSDs. I had an OCZ Vertex 2 die on me multiple times, but one thing that stood out most is that after a power cycle or complete system shutdown (note: reboots were just fine) everything I had done last time - install software, update Windows, create files - was gone. The state was reverted to before the time it booted. It was like my computer contained some kind of Reborn chip, except it was the Sandforce controller malfunctioning.

ricardobeat 8y ago
Modern SSDs can have very large DRAM write buffers (8-256MB), this is pretty plausible if it was failing to flush it.
- Skunkleton 8y ago
  It was probably some kind of wear leveling metadata that didnt get flushed.
deleted 8y ago
[deleted]
yzmtf2008 8y ago
Modern SSDs have incredibly large caches. For example, HP EX920, which is a TLC (triple layer cell) SSD, in its 1TB model contains a whooping 200GB of SLC (single layer cell) cache. It's entirely possible that your changes are simply in cache only, and hasn't been committed to the actual storage.
- undersuit 8y ago
  I don't know if I'm getting exactly what you're saying, but a sudden power off isn't going to wipe your SSD's SLC cache like it would do the DRAM cache on more expensive drives.
  - nightfly 8y ago
    But if the controller gets into a weird state and "forgets" to flush the cache and then doesn't even look at the SLC cache on the next boot...
    - undersuit 8y ago
      The SLC cache is managed by the controller, it's not going to forget to write it to the flash cells being managed as TLC/QLC, the controller is transparently storing your data in both. The controller knows if put some data in the SLC cache and some data in the QLC, and that that data needs to move from SLC to QLC, and that that other data in the SLC was marked deleted so now it can return that entire block to being addressed as QLC. I don't know. I'm just trying to say that since flash isn't volatile the SLC cache isn't treated as volatile cache either.
  - ptman 8y ago
    It's probably more like the superblock not being updated to point to the newest data. Instead it points to old data that hasn't been garbage collected.
blattimwind 8y ago
Like many early adopters, I too had a bunch of failed Vertex 2 drives and sometimes observed similar things. I think this might be because the drive lost some updates to its FTL about where it wrote new data, which could plausibly lead to both new files vanishing and changes to existing ones being apparently undone.
- sebazzz 8y ago
  Yes, the Sandforce controller in Vertex 2 was a real unstable beast. I lost maybe three or four Vertex 2 drives. All under warranty, except the last one which suddenly vanished and was not detected anymore. OCZ does not exist anymore. Not sure of if this was one of the causes, but I would otherwise never buy a drive from them again.

ricardobeat 8y ago

Modern SSDs can have very large DRAM write buffers (8-256MB), this is pretty plausible if it was failing to flush it.

Skunkleton 8y ago
It was probably some kind of wear leveling metadata that didnt get flushed.

deleted 8y ago

[deleted]

yzmtf2008 8y ago

Modern SSDs have incredibly large caches. For example, HP EX920, which is a TLC (triple layer cell) SSD, in its 1TB model contains a whooping 200GB of SLC (single layer cell) cache. It's entirely possible that your changes are simply in cache only, and hasn't been committed to the actual storage.

undersuit 8y ago
I don't know if I'm getting exactly what you're saying, but a sudden power off isn't going to wipe your SSD's SLC cache like it would do the DRAM cache on more expensive drives.
- nightfly 8y ago
  But if the controller gets into a weird state and "forgets" to flush the cache and then doesn't even look at the SLC cache on the next boot...
  - undersuit 8y ago
    The SLC cache is managed by the controller, it's not going to forget to write it to the flash cells being managed as TLC/QLC, the controller is transparently storing your data in both. The controller knows if put some data in the SLC cache and some data in the QLC, and that that data needs to move from SLC to QLC, and that that other data in the SLC was marked deleted so now it can return that entire block to being addressed as QLC. I don't know. I'm just trying to say that since flash isn't volatile the SLC cache isn't treated as volatile cache either.
- ptman 8y ago
  It's probably more like the superblock not being updated to point to the newest data. Instead it points to old data that hasn't been garbage collected.

blattimwind 8y ago

Like many early adopters, I too had a bunch of failed Vertex 2 drives and sometimes observed similar things. I think this might be because the drive lost some updates to its FTL about where it wrote new data, which could plausibly lead to both new files vanishing and changes to existing ones being apparently undone.

sebazzz 8y ago
Yes, the Sandforce controller in Vertex 2 was a real unstable beast. I lost maybe three or four Vertex 2 drives. All under warranty, except the last one which suddenly vanished and was not detected anymore. OCZ does not exist anymore. Not sure of if this was one of the causes, but I would otherwise never buy a drive from them again.