> From: Edward Ned Harvey [mailto:sh...@nedharvey.com] > > Let's crunch some really quick numbers here. Suppose a 6Gbit/sec > sas/sata bus, with 6 disks in a raid-5. Each disk is 1TB, 1000G, and > each disk is capable of sustaining 1 Gbit/sec sequential operations. > These are typical measurements for systems I use. Then 1000G = > 8000Gbit. It will take 8000 sec to resilver = 133min. So whenever > people have resilver times longer than that ... It's because ZFS > resilver code for raidzN is inefficient.
I hate to be the unfortunate one verifying my own point here, but: One of the above mentioned disks needed to be resilvered yesterday. (Actually a 2T disk.) It has now resilvered 1.12T in 18.5 hrs, and has 10.5 hrs remaining. This is a mirror. The problem would be several times worse if it were a raidz. So I guess it's unfair to say "raidz is inefficient at resilvering." The truth is, ZFS in general is inefficient at resilvering, but the problem is several times worse on raidz than it is for mirrors. The more disks in the vdev, the worse the problem. The fewer vdev's in the pool, the worse the problem. So you're able to minimize the problem by using a bunch of mirrors instead of raidzN. Although the problem exists on mirrors too, it's nothing so dramatic that I would destroy & recreate my pool because of it. People with raidzN often do. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
