Hi,
On one of our production email servers, we have a filesystem called /spool
(/var/spool is a symbolic link to /spool). /spool sits on top of a 3-spindle
RAID 0+1 set (re9 - the second RAID set on one of the RAID controllers).
After looking at the output of iostat over a period of time, we think that
waiting for IO requests for /spool to complete might be slowing the amount
of work the system could otherwise be doing. The CPU is about 68% idle, while
iostat is reporting figures around 120 transfers per second, and 4000kb
transferred per second. It has been higher at times, but they are the average
figures. I find it hard to know for sure
if /spool is a bottleneck for the system or not, just by looking at iostat's
output.
In any case, our email administrators have requested that /spool be
reconfigured as two separate two-spindle RAID 0+1 volumes (one on each
RAID controller), joined into a single logical volume with LSM (ie. mirroring
and striping done by the RAID controllers, just the joining of the two into
a single volume done by LSM).
What I'd like to know is, are there any obvious
problems with doing this? Is it likely to give a significant reduction to the
average seek time/time to complete each IO request?
Also, do we need to apply any additional patches, or is LSM straight off the
DU4.0D CD plus PK3 fine?
Additional info:
Operating System: Digital Unix 4.0D PK3
Machine type: AlphaServer 1200 5/533
Firmware: 5.2
Memory: 512Mb
Disk subsystem: 2 * 3 channel RAID controller (I'm not sure of the type)
controlling disks across 3 shelves.
I'm happy to provide additional information, and I'll summarise any replies.
My email address is s.brewster_at_qut.edu.au.
Scott
Received on Wed Sep 08 1999 - 03:12:03 NZST