From: Drew <drew.kay@gmail.com>
To: simon@mcnair.co.uk
Cc: linux-raid@vger.kernel.org
Subject: Re: single threaded parity calculation ?
Date: Sat, 16 Apr 2011 06:45:18 -0700 [thread overview]
Message-ID: <BANLkTims2gPKdxOo4_dd1NAnOz=CcL6yGQ@mail.gmail.com> (raw)
In-Reply-To: <4DA89A18.5010002@mcnair.co.uk>
> iostat reports 83MB/s for each disk, running up to 830MB/s for all 10 disks,
> but the max read speed of the array is approx 256MB/s.
This may be a dumb question but what motherboard & disk controllers
are you using and how are they setup?
That 256MB/s feels to me like you may be bumping up against a
bandwidth limitation of your bus. PCI (32bit/33MHz) is limited to
133MB/s max and PCIe(1.0/2.0) is limited to 250/500MB/s per lane. To
sustain 830MB/s you need at least a PCIe (1.0) x4 or PCI-X 133
controller card which are both rated for (theoretically) 1GB/s.
As an aside, for read speeds on a RAID-5, the parity disk isn't used
so theoretical maximum in this case is 9x83MB/s or 747MB/s. ;-)
--
Drew
"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
next prev parent reply other threads:[~2011-04-16 13:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-15 19:18 single threaded parity calculation ? Simon McNair
2011-04-15 20:54 ` Phil Turmel
2011-04-15 21:28 ` Phil Turmel
2011-04-15 21:44 ` Simon Mcnair
2011-04-15 21:46 ` NeilBrown
2011-04-16 13:45 ` Drew [this message]
2011-04-16 19:07 ` Simon McNair
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