Mirrors are much quicker to replace if one DOES fail though...so i would think that bad stuff could happen with EITHER solution....If you buy a bunch of hard drives for a raidz and they are all from the same batch they might all fail around the same time...what if you have a raidz2 group and 2 drives fail, then you're adding 2 drives back and another fails before it's complete because it takes SO long to resilver? At least with mirrors they resilver fast.
The bottom line is that bad stuff CAN happen and often does...so don't let raidz or mirrors be the only solution you have. Redundancy is good. More redundancy is better... but backups are the best. On Wed, Sep 16, 2009 at 1:23 PM, Richard Elling <richard.ell...@gmail.com>wrote: > On Sep 16, 2009, at 9:38 AM, Marty Scholes wrote: > >> Generally speaking, striping mirrors will be faster >>> than raidz or raidz2, >>> but it will require a higher number of disks and >>> therefore higher cost to >>> The main reason to use >>> raidz or raidz2 instead >>> of striping mirrors would be to keep the cost down, >>> or to get higher usable >>> space out of a fixed number of drives. >>> >> >> While it has been a while since I have done storage management for >> critical systems, the advantage I see with RAIDZN is better fault tolerance: >> any N drives may fail before the set goes critical. >> >> With straight mirroring, failure of the wrong two drives will invalidate >> the whole pool. >> > > This line of reasoning doesn't get you very far. It is much better to take > a look at > the mean time to data loss (MTTDL) for the various configurations. I wrote > a > series of blogs to show how this is done. > http://blogs.sun.com/relling/tags/mttdl > > -- richard > > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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