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From: David Brown <david.brown@hesbynett.no>
To: linux-raid@vger.kernel.org
Subject: Using of RAID10,offset for faster writes
Date: Sat, 09 Apr 2011 14:03:21 +0200	[thread overview]
Message-ID: <inphu9$5kl$1@dough.gmane.org> (raw)

During a discussion about RAID in another context (a Linux newsgroup), I 
began thinking about the speeds of the different RAID10 layouts for 
different usages.  RAID10,far is often the fastest choice for general 
use - you get striped reads for large reads, and access times are good 
because you can get the data from either disk.  The disadvantage is that 
writes involve a lot of extra head movement, as you need copies of the 
data on two widely separated areas on the each disk.  But for general 
use, you read a lot more often than you write, so the tradeoff is worth it.

In the discussion we were looking particularly at swap space on RAID. 
This is a usage that requires a lot of writing, especially small writes. 
  Using the RAID10,offset layout should give you most of the benefits of 
RAID10,far when it comes to reading - you don't get quite as efficient 
block reads for large reads, but you can still do a lot of striping in 
the reads.  And writes will involve far less head movement, and so 
should complete faster.

Has anyone tried this, or done any benchmarking?


             reply	other threads:[~2011-04-09 12:03 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-09 12:03 David Brown [this message]
2011-04-09 15:05 ` Using of RAID10,offset for faster writes Keld Jørn Simonsen
2011-04-10  9:50   ` David Brown

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