One of the obvious big differences between RAID-Z and RAID-5 is that Z can be run on just two disks. I do note it suggests you really want three, but I've run it on two (slices rather than whole disks, in a small test environment) and it works and recovers from removal or severe damage to either of the slices just as advertised.
So the question becomes, what are the tradeoffs between running a two-way mirror vs. running RAID-Z on two disks? It looks like I can replace one of the disks in the RAID-Z with a bigger one, and get more usable space in the pool. I don't believe I can do that in a mirror. That would seem to be a significant benefit for RAID-Z vs. a two-way mirror. Are there corresponding disadvantages? I had hoped to be able to add additional disks into an existing RAID-Z and expand the available space, but that doesn't seem to be possible after all (I kinda got the impression it could from the announcements and summaries, but no command in the manuals seems to let me do anything like that). Oh well. I do see that you can add new RAIDZ, mirrors, or individual disks to the pool, and all the filesystems will draw against the space provided by all the different sources of disk; and of course the reliability will be that of the least reliable. This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
