[zfs-discuss] L2ARC and SLOG on HW RAID with writeback cache

Gionatan Danti g.danti at assyoma.it
Sun Apr 29 16:37:17 EDT 2018


Il 29-04-2018 21:48 Richard Yao via zfs-discuss ha scritto:
> There is nothing in the hardware to protect against this. A
> misdirected write (likely caused by vibration) could be detected if a
> read is done afterward, but that has two problems. The first is that
> nobody does it because it hurts performance. The second is that there
> is no telling where the write went without stopping the world and
> scrutinizing everything (for several hours) and trying to make sense
> of how to fix it, which nobody does. It is in no way practical.

T10 DIF/DIX *does* protect against misredicted writes: 
https://www.usenix.org/legacy/event/lsf07/tech/petersen.pdf
However, it requires expensive SAS controllers, backplanes and disks.

That said, I reiterate: my question about HW RAID was limited to 
SATA-based L2ARC/SLOG.
Any thoughts on that?

Thanks.

-- 
Danti Gionatan
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