[OmniOS-discuss] Status of TRIM support?

[Schweiss, Chip]

The 840 Pro doesn't have a super cap, but it does properly honor cache
flushes which ZFS will do on a log device.   This drastically reduces it's
write performance and makes it a poor choice for a log device.

Intel has several SATA SSDs with proper super-cap protected caches that
make good log devices.   They are nothing like a ZeusRAM, but will protect
your transactions.

Keep in mind vSphere is a 100% sync write NFS client. If the log device
doesn't perform well, neither will vSphere.

If you trust your backups I would stick to ZIL disabled.   If you want to
do HA, you need to look at an all SAS solution, which is not cheap.

-Chip



On Wed, May 28, 2014 at 8:51 AM, Dan Swartzendruber <dswartz at druber.com>wrote:

> (merging comments to Saso and Jim)
>
> I don't think I mentioned my environment - if not, my apologies.  This is
> a SOHO/Lab setup, so things like zeusram are non-starters.  The basic
> network infrastructure is gigabit, so iSCSI ZIL would suck badly, I
> suspect.  As far as over-provisioning the 840PRO, I have it sliced for
> 16GB.  Once it's been running for awhile, I will re-run the disk
> benchmark.  I understand the 840PRO doesn't have a supercap - this was
> basically just a performance analysis to see how it stacks up compared to
> sync=disabled and on-pool ZIL.  If I go this route, I will need to look
> for a decent/affordable unit with supercap.  One other test I can try is
> with a 15K 76GB SAS 2.5-inch drive I salvaged from a dead server.  It
> should have about 1/2 the latency of a 7200rpm sata drive, and if so would
> get me up to about 40MB/sec, which is still not good, but better than
> on-pool ZIL.  I'll find out later.  I have googled a fair amount and there
> seems to be 'work in progress' for TRIM support for ZoL and illumos, but
> no real indication I could find as to when either might support it.
>
>
>
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