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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                                           [email protected]
Senior Technical Consultant         TAOS            http://www.taos.com/
Got some Dr Pepper?                           San Francisco, CA bay area
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