My testbench is a 4 core Opteron (dual 275's) into
two LSI8408E SAS controllers, into 16 Seagate 7200.10 320GB satas.
Redhat ES4.4 (Centos 4.4). A slightly newer parted is needed
than the contemporary of Moses that is shipped with the O/S.
I have a standard burn in script that takes the 4 4-drive raid0's
and puts a GPT label on them, aligns the partitions to stripe
boundary's. It then proceeds to write 8GB files concurrently
onto all 4 raid drives.
Under 188.8.131.52 the write speeds start at 265MB/Sec and decrease
mostly monotonically down to ~160MB/Sec, indicating that
the files start on the outside (fastest tracks) and work in.
All 4 raids are within 7-8MB/Sec of each other (usually they
are identical in speed).
By the time of 2.6.20-rc3, the same testbench shows
a 10% across the board decrease in throughput for writes.
Reads are unaffected.
But now the allocation order for virgin file systems are random,
usually starting at the slow 140MB/Sec, then bouncing up to 220MB/Sec,
then around and around. No two raids get the same write speeds at the
Dave Lloyd (our in-house Idea Guy) looked at the allocation groups...
What data would you like to see?
The run logs from 184.108.40.206 and 2.6.20-rc3?
Want the scripts?
The xfs-debug dumps of a few files?
//E. F. Berkley Shands, MSc//
3668 S. Geyer Road, Suite 300
St. Louis, MO 63127
Direct: (314) 450-5348
Cell: (314) 303-2546
Office: (314) 450-5353
Fax: (314) 450-5354
This e-mail and any documents accompanying it may contain legally
privileged and/or confidential information belonging to Exegy, Inc.
Such information may be protected from disclosure by law. The
information is intended for use by only the addressee. If you are not
the intended recipient, you are hereby notified that any disclosure or
use of the information is strictly prohibited. If you have received
this e-mail in error, please immediately contact the sender by e-mail or
phone regarding instructions for return or destruction and do not use or
disclose the content to others.
[[HTML alternate version deleted]]