On Tue, 30 Mar 2010, Edward Ned Harvey wrote:
But the speedup of disabling the ZIL altogether is
appealing (and would
probably be acceptable in this environment).
Just to make sure you know ... if you disable the ZIL altogether, and you
have a power interruption, failed cpu, or kernel halt, then you're likely to
have a corrupt unusable zpool, or at least data corruption. If that is
indeed acceptable to you, go nuts. ;-)
I believe that the above is wrong information as long as the devices
involved do flush their caches when requested to. Zfs still writes
data in order (at the TXG level) and advances to the next transaction
group when the devices written to affirm that they have flushed their
cache. Without the ZIL, data claimed to be synchronously written
since the previous transaction group may be entirely lost.
If the devices don't flush their caches appropriately, the ZIL is
irrelevant to pool corruption.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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