Cindy wrote: > Mirrored pools are more flexible and generally > provide good performance. > > You can easily create a mirrored pool of two disks > and then add two > more disks later. You can also replace each disk with > larger disks > if needed. See the example below.
There is no dispute that multiple vdevs (mirrors or otherwise) allow changing the drives in a single vdev without requiring a change the whole pool. There also is no dispute that mirrors provide better read iops than any other vdev type. On the other hand, situation after situation exists where 2+ drives offline in a pool leaving the RAIDZ1 and single mirror vdevs in real trouble. As I write this, the first thread in this forum is about an invalid pool because one drive died and another is offline, leaving the pool corrupted. This stuff just happens in the real world with non-DMX-class gear. One major point I read over and over about zfs was that it allowed the same level of protection without needing to spend $35 per GB of storage from an enterprise vendor. The only way to make this happen is with significant redundancy. I choose n+3 redundancy and love it. It's like having two prebuilt hot spares. To achieve n+3 redundnancy with mirrors would require quadrupling the costs and spindle count vs. unprotected storage. It would seem that any vdev with n+1 protection is not adequate protection using sub million dollar storage equipment. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
