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Re: With 4 disks should I go for RAID 5 or RAID 10

From: Bill Moran <wmoran(at)collaborativefusion(dot)com>
To: Mark Mielke <mark(at)mark(dot)mielke(dot)cc>
Cc: david(at)lang(dot)hm, Florian Weimer <fw(at)deneb(dot)enyo(dot)de>, Fernando Hevia <fhevia(at)ip-tel(dot)com(dot)ar>, 'pgsql-performance' <pgsql-performance(at)postgresql(dot)org>
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
Date: 2007-12-27 16:54:44
Message-ID: 20071227115444.07a9af3f.wmoran@collaborativefusion.com (view raw or flat)
Thread:
Lists: pgsql-performance
In response to Mark Mielke <mark(at)mark(dot)mielke(dot)cc>:

> Bill Moran wrote:
> > In response to Mark Mielke <mark(at)mark(dot)mielke(dot)cc>:
> >
> >   
> >> Bill Moran wrote:
> >>     
> >>> I'm fairly sure that FreeBSD's GEOM does.  Of course, it couldn't be doing
> >>> consistency checking at that point.
> >>>       
> >> According to this:
> >>
> >> http://www.freebsd.org/cgi/man.cgi?query=gmirror&apropos=0&sektion=8&manpath=FreeBSD+6-current&format=html
> >>
> >> There is a -b (balance) option that seems pretty clear that it does not 
> >> read from all drives if it does not have to:
> >>     
> >
> > >From where did you draw that conclusion?  Note that the "split" algorithm
> > (which is the default) divides requests up among multiple drives.  I'm
> > unclear as to how you reached a conclusion opposite of what the man page
> > says -- did you test and find it not to work?
> >   
> Perhaps you and I are speaking slightly different languages? :-) When I 
> say "does not read from all drives", I mean "it will happily read from 
> any of the drives to satisfy the request, and allows some level of 
> configuration as to which drive it will select. It does not need to read 
> all of the drives to satisfy the request."

Ahh ... I did misunderstand you.

-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran(at)collaborativefusion(dot)com
Phone: 412-422-3463x4023

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