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Date:      Wed, 9 Oct 1996 08:56:30 -0700 (PDT)
From:      "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
To:        asami@FreeBSD.org (Satoshi Asami)
Cc:        bsdscsi@shadows.aeon.net, pjchilds@imforei.apana.org.au, freebsd-scsi@FreeBSD.org
Subject:   Re: striping/mirroring?
Message-ID:  <199610091556.IAA06884@GndRsh.aac.dev.com>
In-Reply-To: <199610091003.DAA04113@silvia.HIP.Berkeley.EDU> from Satoshi Asami at "Oct 9, 96 03:03:34 am"

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>  * does this work already? (i cant experiment yet, disks are on purchase
>  * list i have to get signed before i get the disks)
> 
> You mean mirroring?  Yes it's working, has been for a few months.
> 
>  * and am i right assuming (some old post listed these) that 128 is the
>  * interleave value that gives me most speed for reads?
> 
> Depends on what kind of reads you are talking about.  For large
> sequential reads (here the size of individual read()s don't matter --
> the "large" refers to the total size that's read in succession) and
> many disks, something a little smaller is usually better, e.g., 32 or
> 64.
> 
> For random reads, it should probably be the size of the read, i.e., if 
> your reads are 16K, then 32 would do the best.  (Unless the read sizes 
> are very large, say 1M or so...in which case, treat this as
> "sequential" as described above.)  Of course, I'm assuming the reads
> occur at offsets that are integer multiples of the read sizes -- if
> not, I guess you want something a little larger to reduce the chance
> of a single read falling between two disks.
> 
> However, since 128 does reasonably well for both reads and writes,
> that is the size I would recommend for normal (read/write) workloads.

Could you please start recommending CG size interleaves (65536 or there
abouts) for people using this for news spools.  I have had several clients
contact me about abizmal performance and they where using 16 to 128 block
interleaves :-( :-( :-(.



-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com



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