Torrey McMahon wrote On 09/19/06 16:29,:
Eric Schrock wrote:
On Mon, Sep 18, 2006 at 02:20:24PM -0400, Torrey McMahon wrote:
1 - ZFS is self consistent but if you take a LUN snapshot then any
transactions in flight might not be completed and the pool - Which
you need to snap in its entirety - might not be consistent. The more
LUNs you have in the pool the more problematic this could get.
Exporting the pool first would probably get around this issue.
This isn't true. The snapshot will be entirely consistent - you will
have just lost the last few seconds of non-synchronous writes.
> When a synchronous write comes in does it wait for other pending i/o to
> complete?
No. The ZFS Intent Log (ZIL) writes out a record for the transacation
(TX_WRITE, TX_ACL, TX_CREATE, TX_TRUNCATE, etc) and any other transactions
that may be dependents.
> Which writes are tagged as synchronous? (Checksums and uberblocks?)
Transactions arrive marked as synchronous with O_DSYNC/O_SYNC/O_RSYNC
or are flushed synchronously as a result of VOP_FSYNC from nfs or fsync.
Neil.
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