Woops! Yes, of course you would want an ampersand in my little
pseudo-script to background the "dd" jobs. My mistake. "seq" is also
one of my favorite commands, but some systems are so stripped-down that
they don't have it!
-James
Tim Gruene wrote:
Interesting and simple way to test the write performance. Simultaneous
writes could then be tested by putting an ampersand ('&') at the end
of the 'dd' command, couldn't they? And if you get tired of typing all
the number, you could use the 'seq' command instead.
Cheers, Tim
/bin/tcsh
set time
foreach file ( 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
22 23 )
dd if=/dev/zero bs=2G count=1 of=/home/username/deleteme$file
end
-James Holton
MAD Scientist
Harry M. Greenblatt wrote:
BS"D
To those hardware oriented:
We have a compute cluster with 23 nodes (dual socket, dual core
Intel servers). Users run simulation jobs on the nodes from the
head node. At the end of each simulation, a result file is
compressed to 2GB, and copied to the file server for the cluster
(not the head node) via NFS. Each node is connected via a Gigabit
line to a switch. The file server has a 4-link aggregated Ethernet
trunk (4Gb/S) to the switch. The file server also has two sockets,
with Dual Core Xeon 2.1GHz CPU's and 4 GB of memory, running RH4.
There are two raid arrays (RAID 5), each consisting of 8x500GB SATA
II WD server drives, with one file system on each. The raid cards
are AMCC 3WARE 9550 and 9650SE (PCI-Express) with 256 MB of cache
memory . When several (~10) jobs finish at once, and the nodes
start copying the compressed file to the file server, the load on
the file server gets very high (~10), and the users whose home
directory are on the file server cannot work at their stations.
Using nmon to locate the bottleneck, it appears that disk I/O is the
problem. But the numbers being reported are a bit strange. It
reports a throughput of only about 50MB/s, and claims the "disk" is
100% busy. These raid cards should give throughput in the several
hundred MB/s range, especially the 9650 which is rated at 600MB/s
RAID 6 write (and we have RAID 5).
1) Is there a more friendly system load monitoring tool we can use?
2) The users may be able to stagger the output schedule of their
jobs, but based on the numbers, we get the feeling the RAID arrays
are not performing as they should. Any suggestions?
Thanks
Harry
-------------------------------------------------------------------------
Harry M. Greenblatt
Staff Scientist
Dept of Structural Biology [EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
Weizmann Institute of Science Phone: 972-8-934-3625
Rehovot, 76100 Facsimile: 972-8-934-4159
Israel
