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I don't think you get what I'm saying. The bit rot that happens to your data usually happens when it's in the RAM. The CPU likes it there when you're doing anyt
by shouldbworking 9y ago
I don't think you get what I'm saying. The bit rot that happens to your data usually happens when it's in the RAM. The CPU likes it there when you're doing anything with it and once you're done editing a file it will stream happily corrupted data right back to disk. Hard drive and SSD error detection and correction is quite good, in regular ram its non existent.
This is a major danger with database servers, as regular bit rot can be detected or corrected above the filesystem level, but no systems exist that can garantee protection to data in ram. Since databases try to do most/all operations in ram before flushing to disk there's a huge risk of silent data corruption.
Adding bitrot protection to the filesystem only gives you more protection if the drive has crappy error correction. Adding protection to ram adds checks to a system that usually has none
- gbrown_ 9y ago> The bit rot that happens to your data usually happens when it's in the RAM. Would love to read a source on this.
- SamReidHughes 9y agoDisks have their own block checksumming so they can catch errors.
- wtallis 9y agoJust check your disk's SMART indicators for unrecoverable errors. Drives are using pretty high quality checksums on data at rest; the chance of corruption silently slipping past both the BCH and LDPC codes used by a typical modern SSD is far smaller than the chance of your non-ECC RAM getting corrupted by cosmic rays.
- PhantomGremlin 9y agoYour statement is correct, but doesn't tell the rest of the story. The disk has an onboard data buffer, usually implemented in DRAM. That DRAM chip is likely sourced by the lowest bidder, and it is likely not to have either parity or ECC. Also the CPU used in the drive can introduce its own data errors and corruption. It doesn't even have to be hardware. A firmware bug can also corrupt data. There are numerous buffers and storage elements involved in transferring the data to/from the disk's onboard memory to/from the computer's RAM. Many/most of those elements are not checked for parity. Data is subject to corruption in transit. That's what makes a filesystem like ZFS so interesting. It checks the entire data path. It doesn't care where the corruption occurs.
- shouldbworking 9y agoI never considered DRAM errors on the drive... Maybe that's one of the big cost differentiators of those super expensive commercial grade SSDs.