Am 09.08.10 17:22, schrieb Eric Luyten: > Folks, > > A question for those of you running ZFS as the filesystem architecture > for your Cyrus message store : did you consider, measure and/or carry > out a change of the default 128 KB blocksize ? > If so, what value are you using ?
First: Changes to ZFS recordsize do not change the on-disk-format of your zfs/zpool. It just applies to NEWLY created files or file parts/zfs records (!). Second: As said on a ZFS volume the recordsize is NOT the block size. The record size is the size of a single ZFS record read at once. Due to the ZIL changes to files get written nearly sequentially so the recordsize is nearly irrelevant. A smaller record size is a good option if you notice an i/o bottleneck on your fiberchannel/iSCSI/SAS link. It won't bring you a performance gain in random i/o. There is a small exception: Database systems writing always the same fixed blocksize. For MySQL some people advise 32k. ZFS record size is not the same as zfs block size of a zvol (zfs block volume). That's another story. But I assume you are not talking about a ZFS block volume iSCSI server with a non-zfs-filesystem written on it. Just my $0.02, Pascal ---- Cyrus Home Page: http://cyrusimap.web.cmu.edu/ Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
