On Mon, 16 Jul 2012, Michael Hase wrote:

This is my understanding of zfs: it should load balance read requests even for a single sequential reader. zfs_prefetch_disable is the default 0. And I can see exactly this scaling behaviour with sas disks and with scsi disks, just not on this sata pool.

Is the BIOS configured to use AHCI mode or is it using IDE mode?

Are the disks 512 byte/sector or 4K?

Maybe it's a corner case which doesn't matter in real world applications? The random seek values in my bonnie output show the expected performance boost when going from one disk to a mirrored configuration. It's just the sequential read/write case, that's different for sata and sas disks.

I don't have a whole lot of experience with SATA disks but it is my impression that you might see this sort of performance if the BIOS was configured so that the drives were used as IDE disks. If not that, then there must be a bottleneck in your hardware somewhere.

Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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