> > But, is there a performance boost with mirroring the drives? That is what > > I'm unsure of. > > Mirroring will provide a boost on reads, since the system to read from > both sides of the mirror. It will not provide an increase on writes, > since the system needs to wait for both halves of the mirror to > finish. It could be slightly slower than a single raid5.
That's not strictly correct. Mirroring will, in fact, deliver better IOPS for both reads and writes. For reads, as Brandon stated, mirroring will deliver better performance because it can distribute the reads between both devices. For writes, however, RAID-Z with an N+1 wide stripe will divide the the data into N+1 chunks, and reads will need to access the N chunks. This reduces the total IOPS by a factor of N+1 for reads and writes whereas mirroring reduces the IOPS by a factor of 2 for writes and not at all for reads. Adam -- Adam Leventhal, Fishworks http://blogs.sun.com/ahl _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
