On Apr 18, 2007, at 2:35 AM, Richard L. Hamilton wrote:
Well, no; his quote did say "software or hardware". The theory is
apparently
that ZFS can do better at detecting (and with redundancy,
correcting) errors
if it's dealing with raw hardware, or as nearly so as possible.
Most SANs
_can_ hand out raw LUNs as well as RAID LUNs, the folks that run
them are
just not used to doing it.
Another issue that may come up with SANs and/or hardware RAID:
supposedly, storage systems with large non-volatile caches will
tend to have
poor performance with ZFS, because ZFS issues cache flush commands as
part of committing every transaction group; this is worse if the
filesystem
is also being used for NFS service. Most such hardware can be
configured to ignore cache flushing commands, which is safe as long as
the cache is non-volatile.
The non-volatile cache issues are being covered by:
6462690 sd driver should set SYNC_NV bit when issuing SYNCHRONIZE
CACHE to SBC-2 devices
PSARC 2007/053
The PSARC case has been approved, and Grant is finishing up the code
changes.
eric
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