Kjetil Torgrim Homme <kjeti...@linpro.no> writes: > Cindy Swearingen <cindy.swearin...@sun.com> writes: >> You might check the slides on this page: >> >> http://hub.opensolaris.org/bin/view/Community+Group+zfs/docs >> >> Particularly, slides 14-18. >> >> In this case, graphic illustrations are probably the best way >> to answer your questions. > > thanks, Cindy. can you explain the meaning of the blocks marked X in > the illustration on page 18?
I found the explanation in an older (2009-09-03) message to this list from Adam Leventhal: | RAID-Z writes full stripes every time; note that without careful | accounting it would be possible to effectively fragment the vdev | such that single sectors were free but useless since single-parity | RAID-Z requires two adjacent sectors to store data (one for data, | one for parity). To address this, RAID-Z rounds up its allocation to | the next (nparity + 1). This ensures that all space is accounted | for. RAID-Z will thus skip sectors that are unused based on this | rounding. For example, under raidz1 a write of 1024 bytes would | result in 512 bytes of parity, 512 bytes of data on two devices and | 512 bytes skipped. -- Kjetil T. Homme Redpill Linpro AS - Changing the game _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
