On Thu, Sep 13, 2007 at 12:56:44AM +0200, Pawel Jakub Dawidek wrote: > On Wed, Sep 12, 2007 at 11:20:52PM +0100, Peter Tribble wrote: > > My understanding of the raid-z performance issue is that it requires > > full-stripe reads in order to validate the checksum. [...] > > No, checksum is independent thing, and this is not the reason why RAIDZ > needs to do full-stripe reads - in non-degraded mode RAIDZ doesn't read > parity.
I doubt reading the parity could cost all that much (particularly if there's enough I/O capacity). It's reading the full 128KB that you have to read, if a file's record size is 128KB, in order to satisfy a 2KB read. And ZFS has to read full blocks in order to verify the checksum. Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
