>>>>> "sm" == Scott Meilicke <no-re...@opensolaris.org> writes:
sm> Some storage will flush their caches despite the fact that the
sm> NVRAM protection makes those caches as good as stable
sm> storage. [...] ZFS also issues a flush every time an
sm> application requests a synchronous write (O_DSYNC, fsync, NFS
sm> commit, and so on). [...] this neutralizes the benefits of
sm> having an NVRAM-based storage."
if the external RAID array or the solaris driver is broken, yes. If
not broken, the NVRAM should provide an extra-significant speed boost
for exactly the case of frequent synchronous writes. Isn't that
section of the evil tuning guide you're quoting actually about
checking if the NVRAM/driver connection is working right or not?
sm> When I was testing iSCSI vs. NFS, it was clear iSCSI was not
sm> doing sync, NFS was.
I wonder if this is a bug in iSCSI, in either the VMWare initiator or
the Sun target. With VM's there shouldn't be any opening and closing
of files to provoke an extra sync on NFS, only read, write, and sync
to the middle of big files, so I wouldn't think NFS should do any more
or less syncing than iSCSI.
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