Roch Bourbonnais wrote: > > Le 28 févr. 08 à 21:00, Jonathan Loran a écrit : > >> >> >> Roch Bourbonnais wrote: >>> >>> Le 28 févr. 08 à 20:14, Jonathan Loran a écrit : >>> >>>> >>>> Quick question: >>>> >>>> If I create a ZFS mirrored pool, will the read performance get a >>>> boost? >>>> In other words, will the data/parity be read round robin between the >>>> disks, or do both mirrored sets of data and parity get read off of >>>> both >>>> disks? The latter case would have a CPU expense, so I would think you >>>> would see a slow down. >>>> >>> >>> 2 disks mirrored together can read data faster than a single disk. >>> So to service a read only one side of the mirror is read. >>> >>> Raid-Z parity is only read in the presence of checksum errors. >> That's what I suspected, but I'm glad to get the final word on this. >> BTW, I guess I should have said checksums instead of parity. My bad. >> > > OK. The checksum is a different story and is stored within the > metadata block pointing to the data block. > So given that to reach the data block we've already had to read the > metadata block, checskum validation is never the > source of an I/O. I really need to read those ZFS internals docs (in all my spare time ;) Thanks,
Jon _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
