Erik Trimble wrote:
Yes, if you stick (say) a 1.5TB, 1TB, and .5TB drive together in a RAIDZ, you will get only 1TB of usable space. Of course, there is always the ability to use partitions instead of the whole disk, but I'm not going to go into that. Suffice to say, RAIDZ (and practically all other RAID controllers, and volume managers) don't easily deal maximizing space with different size disks.
In the example above, The best you can get out of ZFS is 1.5TB. You'd get that by creating 2 mirrors - a (.5TB of 1.5TB partition) + .5TB mirror, and a (1TB of 1.5TB partition) + 1TB mirror. I _think_ that's also the best you can get, period, but I may be wrong. The absolute cap is 2TB (2/3 of the 3TB total), but in that spindle config I think the cap is 1.5TB.
While the "figure it out for me and make it as big as you can while still being safe" magic of drobo is nice for home users, it's less than ideal for enterprise users that require performance guarantees.
It would be nice if somebody created a simple tool that, fed a set of disks, computed the configuration required for maximum usable redundant space.
-- Carson _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
