On 04/07/10 10:18, Edward Ned Harvey wrote:
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Bob Friesenhahn
It is also worth pointing out that in normal operation the slog is
essentially a write-only device which is only read at boot time. The
writes are assumed to work if the device claims "success". If the log
device fails to read (oops!), then a mirror would be quite useful.
An excellent point.
BTW, does the system *ever* read from the log device during normal
operation? Such as perhaps during a scrub? It really would be nice to
detect failure of log devices in advance, that are claiming to write
correctly, but which are really unreadable.
A scrub will read the log blocks but only for unplayed logs.
Because of the transient nature of the log and becuase it operates
outside of the transaction group model it's hard to read the in-flight
log blocks
to validate them.
There have previously been suggestions to read slogs periodically.
I don't know if there's a CR raised for this though.
Neil.
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