On Wed, Jul 21, 2010 at 7:43 PM, Edward Ned Harvey <sh...@nedharvey.com> wrote: >> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- >> boun...@opensolaris.org] On Behalf Of John Andrunas >> >> I know this is potentially a loaded question, but what is generally >> considered the optimal disk configuration for ZFS. I have 48 disks on >> 2 RAID controllers (2x24). The RAID controller can do RAID >> 0/1/5/6/10/50/60 or JBOD. What is generally considered the optimal >> configuration for the disks. JBOD, RAID zvols on both controllers. > > No matter what your goals are, you should JBOD the disks, and let ZFS manage > the raid. It not only performs better than hardware raid, it's also more > reliable. When you scrub, ZFS will be able to access all the bytes on all > the disks. But if you had something like a hardware mirror, the hardware > would only present a single device to the OS, and therefore the OS wouldn't > be able to scrub all the bits on both sides of the mirror. If there's a > data error encountered in hardware mirror, ZFS has no 2nd device to read > from to correct the error. All it can do is blindly retry the hardware, and > hope for a different answer. Which probably isn't going to happen. > > Generally speaking, your choices are: > Stripe, Mirror, Stripe & Mirror, or Raid(z,z2,z3)
You forgot "stripe & raidz", aka a pool with multiple raidz vdevs. > Generally speaking, raid has the capacity of n-1, n-2, or n-3 disks > depending on which config you choose. It performs just as fast (n-1, n-2, > or n-3) for large sequential operations. But the performance for small > random operations is poor. Maybe 1 disk or 2 disks performance. Raid is > usually what you use when you need high capacity, and you need redundancy, > and you're budget constrained. You are forced to sacrifice some speed. You > could have gotten better performance by striping mirrors, but then you'd > have to spend more money on disks to have the same usable space. And, adding multiple raidz vdevs (each with under 10 disks) to a single pool (aka stripe of raidz) will give better performance than a single large raidz vdev. -- Freddie Cash fjwc...@gmail.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
