2012-01-21 19:18, Bob Friesenhahn wrote:
On Sat, 21 Jan 2012, Jim Klimov wrote:

5) It seems like a worthy RFE to include a pool-wide option to
"verify-after-write/commit" - to test that recent TXG sync
data has indeed made it to disk on (consumer-grade) hardware
into the designated sector numbers. Perhaps the test should
be delayed several seconds after the sync writes.

This is an interesting idea. I think that you would want to do a
mini-scrub on a TXG at least one behind the last one written since
otherwise any test would surely be foiled by caching. The ability to
restore data from RAM is doubtful since TXGs get forgotten from memory
as soon as they are written.

That could be rearranged as part of the bug/RFE resolution ;)

Regarding the written data, I believe it may find place in the
ARC, and a for the past few TXGs it could still remain there.
I am not sure it is feasible to "guarantee" that it remains in
RAM for a certain time. Also there should be a way to enforce
media reads and not ARC re-reads when verifying writes...


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