Problem solved; I sent Bruce 2 relevant papers from CMU and FAST 2009.
/Sorin
On Tue, 08 Jun 2010 02:54:53 -0400, Benny Halevy <bhalevy@xxxxxxxxxxx>
wrote:
On 2010-06-07 21:49, J. Bruce Fields wrote:
On Mon, Jun 07, 2010 at 09:41:29PM +0300, Boaz Harrosh wrote:
On 06/07/2010 09:29 PM, J. Bruce Fields wrote:
On 06/07/2010 07:07 PM, Boaz Harrosh wrote:
I did not yet publish the Document. It's stuck behind my
dis-talent for
writing and the pnfs bugs de jur.
Untalented writing we can fix, as long as the details are there!
Basically all machines:
- connected by a 1 GBit link.
- All clients doing a dd write of 8GB file from /dev/zero
- 3of8 is the special raid-groups arrangement of exofs && objlayout
where out of 8 devices each file is striped over 3 devices in a
round robin fashion. (*With a small dirty trick)
Random stupid questions:
- why do you think the 3of8 arrangement is scaling better than
the 8of8?
It's a know problem with a network storage cluster. What happens is
that with 8of8 all the clients exercise all of the nodes at the same
time so they are clashing on the network.
OK, so if two clients are both trying to send a stripe of data to the
same OSD data at the same time, absent a switch that could somehow
afford to queue up a full stripe-unit's worth of data, packets get lost?
(Also, out of curiosity: do you know of any papers or documentation that
describe that problem in more detail?)
A good place to start would be
http://www.pdl.cmu.edu/Incast/
Benny
--b.
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Best Regards
Sorin Faibish
Corporate Distinguished Engineer
Network Storage Group
EMC²
where information lives
Phone: 508-435-1000 x 48545
Cellphone: 617-510-0422
Email : sfaibish@xxxxxxx
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