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 <dswa...@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. > > > > _______________________________________________ > OmniOS-discuss mailing list > OmniOS-discuss@lists.omniti.com > http://lists.omniti.com/mailman/listinfo/omnios-discuss >
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