3 ms·
> The point is there's no need to move blocks, just stop writing to worn-out blocks, and then the CoW nature of the filesystem will take care of the rest. Supp
by mgerdts 4y ago
> The point is there's no need to move blocks, just stop writing to worn-out blocks, and then the CoW nature of the filesystem will take care of the rest.
Suppose the file system stores photos and videos that the owner tends to keep forever without ever modifying them. The first files will land on NAND blocks with close to zero PE cycles and will stay there forever. Since they are never modified CoW will never cause them to stop squatting. If the drive fills with content like this endurance doesn’t matter unless there’s a crazy amount of atime updates.
If the static photo and video collection grows to occupy 75% of the space and a more dynamic workload uses some portion of the remaining 25%, about 75% of the drive’s endurance is not accessible.
- cryptonector 4y agoThat's a problem with the SSD's controller. Wearing out in principle should only render cells read-only. But some SSDs are more aggressive.
- rasz 4y agoFTL handles this case by silently moving data around. Cold data retention is REALLY BAD in modern NAND generations using increasingly smaller geometries. Degraded data requires multiple slower reads. Samsung even had to deploy emergency FW update to make this process more aggressive on 840 evo where drive slowed to a crawl reading >1 year old data. https://www.techspot.com/news/60501-samsung-addresses-slow-840-evo-ssd.html https://www.techspot.com/news/60501-samsung-addresses-slow-8...