5 ms·

As a ZFS user: quite useful. I’ve had numerous of cases of corruption repaired by routine scrubs. Almost every other filesystem (btrfs being an exception afaik)

As a ZFS user: quite useful. I’ve had numerous of cases of corruption repaired by routine scrubs. Almost every other filesystem (btrfs being an exception afaik) would have been none the wiser.

ksec 5y ago
Useful for HDD, but on SSD? When both the NAND and Controller has Error Correction?
- rhn_mk1 5y ago
  It's just as useful on either. Error correction predates SSDs.
- magicalhippo 5y ago
  Errors can happen during transmission as well, especially if cables or backplanes are involved.
- etbe 5y ago
  In addition to cables and backplanes that have been mentioned, the entire path from RAM to PCIe to disk controller has non zero risks of errors. That said I'm pretty sure that the BTRFS errors I've seen from SSDs have all been the fault of the SSDs in question. Also note that hard drives have had internal error detection and correction codes for decades, so SSDs doesn't change things much. Probably most checksum errors are misplaced writes and missing writes.
- MertsA 5y ago
  HDDs also use ECC hence why read errors occur on failing drives instead of just silently returning corrupt data. That's not an ironclad guarantee and plenty of places in the data path can let an errant cosmic ray flip bits. BTRFS doesn't even eliminate this, it just reduces the surface area and most importantly gives you a way to durably detect or correct this from when the checksum is generated in the kernel onwards.
hardwaresofton 5y ago
+1, having the visibility (and the ability to correct it) is also often a leading indicator of drive failure. I would argue though that at this point most other filesystems have this, but they're not as ergonomic/obviously built in. LVM has integrity checking at the volume level (if you give drives to the pool instead of giving the pool an already-RAIDed device), mdraid has dm-integrity. The options are there but not quite as discoverable.

As a ZFS user: quite useful. I’ve had numerous of cases of corruption repaired by routine scrubs. Almost every other filesystem (btrfs being an exception afaik) would have been none the wiser.

ksec 5y ago

Useful for HDD, but on SSD? When both the NAND and Controller has Error Correction?

rhn_mk1 5y ago
It's just as useful on either. Error correction predates SSDs.
magicalhippo 5y ago
Errors can happen during transmission as well, especially if cables or backplanes are involved.
etbe 5y ago
In addition to cables and backplanes that have been mentioned, the entire path from RAM to PCIe to disk controller has non zero risks of errors. That said I'm pretty sure that the BTRFS errors I've seen from SSDs have all been the fault of the SSDs in question. Also note that hard drives have had internal error detection and correction codes for decades, so SSDs doesn't change things much. Probably most checksum errors are misplaced writes and missing writes.
MertsA 5y ago
HDDs also use ECC hence why read errors occur on failing drives instead of just silently returning corrupt data. That's not an ironclad guarantee and plenty of places in the data path can let an errant cosmic ray flip bits. BTRFS doesn't even eliminate this, it just reduces the surface area and most importantly gives you a way to durably detect or correct this from when the checksum is generated in the kernel onwards.

hardwaresofton 5y ago

+1, having the visibility (and the ability to correct it) is also often a leading indicator of drive failure. I would argue though that at this point most other filesystems have this, but they're not as ergonomic/obviously built in. LVM has integrity checking at the volume level (if you give drives to the pool instead of giving the pool an already-RAIDed device), mdraid has dm-integrity. The options are there but not quite as discoverable.