According to a Sun document called something like 'ZFS best practice' I read some time ago, best practice was to use the entire disk for ZFS and not to partition or slice it in any way. Does this advice hold good for FreeBSD as well?

I looked at a server earlier this week that was running FreeBSD 8.0 and had 2 x 1 Tb SAS disks in a ZFS 13 mirror with a third identical disk as a spare. Large file I/O throughput was OK but the mail jail it hosted had periods when it was very slow with accessing lots of small files. All three disks (the two in the ZFS mirror plus the spare) had been partitioned with gpart so that partition 1 was a 6 GB swap and partition 2 filled the rest of the disk and had a 'freebsd-zfs' partition on it. It was these second partitions that were part of the mirror.

This doesn't sound like a very good idea to me as surelt disk seeks for swap and for ZFS file I/O are bound to clash. aren't they?

Another point about the Sun ZFS paper - it mentioned optimum performance would be obtained with RAIDz pools if the number of disks was between 3 and 9. So I've always limited my pools to a maximum of 9 active disks plus spares but the other day someone here was talking of seeing hundreds of disks in a single pool! So what is the current advice for ZFS in Solaris and FreeBSD?

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