On Sep 11, 2008, at 11:19 AM, A Darren Dunham wrote: > On Thu, Sep 11, 2008 at 10:33:00AM -0400, Jim Dunham wrote: >> The issue with any form of RAID >1, is that the instant a disk fails >> out of the RAID set, with the next write I/O to the remaining members >> of the RAID set, the failed disk (and its replica) are instantly out >> of sync. > > Does raidz fall into that category?
Yes. The key reason is that as soon as ZFS (or other mirroring software) detects a disk failure in a RAID >1 set, it will stop writing to the failed disk, which also means it will also stop writing to the replica of the failed disk. From the point of view of the remote node, the replica of the failed disk is no longer being updated. Now if replication was stopped, or the primary node powered off or panicked, during the import of the ZFS storage pool on the secondary node, the replica of the failed disk must not be part of the ZFS storage pool as its data is stale. This happens automatically, since the ZFS metadata on the remaining disks have already given up on this member of the RAID set. > Since the parity is maintained only > on written blocks rather than all disk blocks on all columns, it seems > to be resistant to this issue. > > -- > Darren > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss Jim Dunham Engineering Manager Storage Platform Software Group Sun Microsystems, Inc. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
