2012-01-22 0:55, Bob Friesenhahn wrote:
On Sun, 22 Jan 2012, Jim Klimov wrote:
So far I rather considered "flaky" hardware with lousy
consumer qualities. The server you describe is likely
to exceed that bar ;)

The most common "flaky" behavior of consumer hardware which causes
troubles for zfs is not honoring cache-related requests. Unfortunately,
it is not possible for zfs to fix such hardware. Zfs works best with
hardware which does what it is told.

Also true. That's what the "option" stood for in my proposal:
since the verification feature is going to be expensive and
add random IOs, we don't want to enforce it on everybody.

Besides, the user might choose to trust his reliable and
expensive hardware like a SAN/NAS with battery-backed NVRAM,
which is indeed likely better that a homebrewn NAS box with
random HDDs thrown in with no measure, but with a desire for
some reliability nonetheless ;)

We can "expect" the individual HDDs caches to get expired
after some time (i.e. after we've sent 64Mbs worth of writes
to the particualr disk with a 64Mb cache), and after that
we are likely to get true media reads. That's when the
verification reads are likely to return most relevant
(ondisk) sectors...

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