From: Stan Hoeppner <stan@hardwarefreak.com>
To: xfs@oss.sgi.com
Subject: Re: XFS/Linux Sanity check
Date: Wed, 04 May 2011 05:36:31 -0500 [thread overview]
Message-ID: <4DC12C2F.8060800@hardwarefreak.com> (raw)
In-Reply-To: <BANLkTikNkErCS4q41ajTLa2yJnD8uehY-w@mail.gmail.com>
On 5/3/2011 11:05 AM, Paul Anderson wrote:
> I'm still perfectly willing to buy good HW RAID cards, don't get me
> wrong, but their main benefit to me will be the battery backed cache,
> not the performance.
Good RAID cards have many more advantages than battery cache and
performance. One is moving a RAID card and its attached arrays from a
failed host to a new one. In the case of the hardware RAID card usually
all that is required is loading the HBA driver and mounting the
filesystem. Such a move of an mdraid array is usually, well, not nearly
as straightforward, to put it kindly.
> Keep in mind that it is hard to balance a HW RAID card across multiple
> SAS expanders -you can certainly get a -16e card of some sort, but
> then it does ALL of the I/O to those 4 expanders ALL of the time.
I'm note sure I know exactly what you mean here Paul. You seem to be
talking about RAID card <-> drive chassis cabling flexibility and
symmetrical bandwidth. The following two SAS expander/switch products
are likely worth a quick read:
http://www.intel.com/Products/Server/RAID-controllers/re-res2sv240/RES2SV240-Overview.htm
http://www.lsi.com/channel/products/switch/sas6160/index.html
Using an LSI 9260-4i single 8087 port RAID card, the Intel expander, and
some 8087/8088 panel converters, one could attach *5* x 24 drive LSI
620J SAS JBOD chassis for a total of 120 drives with equal bandwidth
to/from all drives, about 2GB/s total bandwidth, RAID ASIC limited. Few
would want to connect 120 drives to such a single port RAID controller,
but this example demonstrates that symmetry can be achieved across a
large number of cascaded SAS expander ASICs (6 total) with a lot of drives.
--
Stan
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next prev parent reply other threads:[~2011-05-04 10:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-02 15:47 XFS/Linux Sanity check Paul Anderson
2011-05-02 17:09 ` Andi Kleen
2011-05-02 17:13 ` Emmanuel Florac
2011-06-11 1:33 ` FYI: LSI rebuilding; and XFS speed V. raw - hints on maxing out 'dd'....(if not already obvious) Linda Walsh
2011-06-11 9:30 ` Emmanuel Florac
2011-06-11 16:48 ` Linda Walsh
2011-05-03 3:18 ` XFS/Linux Sanity check Dave Chinner
2011-05-03 8:58 ` Michael Monnerie
2011-05-03 16:05 ` Paul Anderson
2011-05-04 10:36 ` Stan Hoeppner [this message]
2011-05-04 6:18 ` Stan Hoeppner
2011-05-04 1:10 ` Stan Hoeppner
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