> Data in raidz2 is striped so that it is split across multiple disks. Partial truth. Yes, the data is on more than one disk, but it's a parity hash, requiring computation overhead and a write operation on each and every disk. It's not simply striped. Whenever you read or write, you need to access all the disks (or a bunch of 'em) and use compute cycles to generate the actual data stream. I don't know enough about the underlying methods of calculating and distributing everything to say intelligently *why*, but I know this:
> In this (sequential) sense it is faster than a single disk. Whenever I benchmark raid5 versus a mirror, the mirror is always faster. Noticeably and measurably faster, as in 50% to 4x faster. (50% for a single disk mirror versus a 6-disk raid5, and 4x faster for a stripe of mirrors, 6 disks with the capacity of 3, versus a 6-disk raid5.) Granted, I'm talking about raid5 and not raidz. There is possibly a difference there, but I don't think so. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
