FS of choice for max random iops ( Maildir )

Terje Elde terje at elde.net
Fri Sep 16 13:36:11 UTC 2011

On 16. sep. 2011, at 12:31, freebsd at 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. 


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