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Re: [zfs-discuss] Re: 6 disk raidz2 or 3 stripe 2 way mirror

Subject: Re: [zfs-discuss] Re: 6 disk raidz2 or 3 stripe 2 way mirror
From: Darren Dunham
Date: Mon, 18 Jun 2007 13:28:28 -0700 PDT
> > If you have the same type and columns, then you have the same
> > availability expectations.  If instead you take a 5 disk raidz and add a
> > 2 disk stripe, you're dramatically changing the availability
> > expectations.  So the force is required.
> Certainly, but adding a mirror doesn't degrade the availability expectations,
> so it's a fairly safe addition.

Nonetheless, it's different.  It does change the cost expectations, so
you could consider that it's a warning for that reason then.  

> I'm sure this is far from simple, but it would be interesting to see zfs
> able to figure out the relative performance characteristics of each of
> its vdevs and spread the load accordingly. :)

There are quite a few ideas around that.  Simply the ability to
recognize "slow" storage would be a good idea.  Then you can make other
decisions (lower it for write priority?  temporarily not use it for
writes?  Decide it's so bad that you should fail it?....)  

Darren Dunham                                           ddunham@xxxxxxxx
Senior Technical Consultant         TAOS            http://www.taos.com/
Got some Dr Pepper?                           San Francisco, CA bay area
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