On 16.09.2011 15:57, free...@top-consulting.net wrote: > Quoting Terje Elde <te...@elde.net>: > >> On 16. sep. 2011, at 12:31, free...@top-consulting.net wrote: >>> Right now I defined an entire array of 8TB ( all 16 disks ) separated >>> in two pieces. 50 GB for FreeBSD to boot and the rest available to >>> configure as storage. >> >> ZFS will want to write to it's ZIL (zfs intent log) before writing to >> the final location of the data. Even if you're not waiting for the >> ZIL-write to disk (because of the controller ram), those writes will >> probably make it through to disk. That gives you twice as many writes >> to disk, and a lot more seek. >> >> If you want to take zfs for a proper spin, I'd like to sugget adding >> two small SSDs to the setup, mirrored by zfs. You can use those both >> for the ZIL, and also as cache, for the array. That's a fairly small >> investment these days, and I would be surprised if it didn't >> significantly improve performance, both for your benchmark, and real >> load. >> >> Note: you might be in trouble if you loose your ZIL, thus the doubling >> up. I *think* you can SSD a cache without risking dataloss, but don't >> take my word for it. >> >> Terje > > I know it's usually a big no-no but since I have the battery backed-up > write cache from the raid card, can't I just disable the ZIL entirely ?
No. However, you could allow the ZIL to be written to a logical disk
with the battery-backed cache.
//Svein
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A: Because it fouls the order in which people normally read text.
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