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Date: Wed, 10 Oct 2012 16:57:47 +0200
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Subject: Re: A little RAID experiment
From: Stefan Ring <stefanrin@gmail.com>
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To: Linux fs XFS <xfs@oss.sgi.com>

Btw, one of our customers recently aquired new gear with HP SmartArray
Gen8 controllers. Now they are something to get excited about! This is
the kind of write performance I would expect from an expensive server
product. Check this out (this is again my artificial benchmark as well
as random write of 4K blocks):

SmartArray P400, 6 300G disks (10k, SAS) RAID 6, 256M BBWC:

ag4
Read 0b  Written 161.56Mb  Total transferred 161.56Mb  (5.3853Mb/sec)
 1378.63 Requests/sec executed

random write
Read 0b  Written 97.578Mb  Total transferred 97.578Mb  (3.2526Mb/sec)
  832.66 Requests/sec executed

SmartArray Gen8, 8 300G disks (15k, SAS) RAID 5, 2GB FBWC:

ag4
Read 0b  Written 2.4575Gb  Total transferred 2.4575Gb  (83.883Mb/sec)
21474.03 Requests/sec executed

random write
Read 0b  Written 343.86Mb  Total transferred 343.86Mb  (11.462Mb/sec)
 2934.24 Requests/sec executed

So yeah, the disks are a bit faster. But what does that matter when
there is such a huge difference otherwise?

Unfortunately, while composing this text, I noticed that the new one
is configured as RAID 5, and I cannot change it because of HP's
licensing policy. That makes it not a meaningful comparison, although
extrapolation from previous SmartArray controllers would suggest that
the RAID5 and RAID6 performance is comparable.

My subjective impression is still a very good one!

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