On Mon, Apr 02, 2007 at 12:37:24AM -0700, homerun wrote: > Is it possible to convert live 3 disks zpool from raidz to raidz2 > And is it possible to add 1 new disk to raidz configuration without > backups and recreating zpool from scratch.
The reason that's not possible is because RAID-Z uses a variable stripe width. This solves some problems (notably the RAID-5 write hole [1]), but it means that a given 'stripe' over N disks in a raidz1 configuration may contains as many as floor(N/2) parity blocks -- clearly a single additional disk wouldn't be sufficient to grow the stripe properly. It would be possible to have a different type of RAID-Z where stripes were variable-width to avoid the RAID-5 write hole, but the remainder of the stripe was left unused. This would allow users to add an additional parity disk (or several if we ever implement further redundancy) to an existing configuration, BUT would potentially make much less efficient use of storage. Adam [1] http://blogs.sun.com/bonwick/entry/raid_z -- Adam Leventhal, Solaris Kernel Development http://blogs.sun.com/ahl _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
