Mark,
here are the stats I just collected on my z/VM 5.2 install running RHEL 4U4.
time dd bs=1024 count=1048576 if=/dev/zero of=/test1
1048576+0 records in
1048576+0 records out
real 0m44.681s
user 0m0.090s
sys 0m6.810s
This is leveraging 3390-3 devices.
As for my issue where I have a user running an environment that is
running far slower, it turns out they are running into I/O contention.
they are running MOD-27 devices so there is a great deal of blocking.
The devices are not dedicated so they can't use PAV and finally it looks
like they have set up the Linux guests with a single CPU. So in general
it looks like some design tweaking and their performance should improve.
Thanks!
Eric
Mark Perry wrote:
Eric and Barbara Sammons wrote:
Looking into performance problems, in search of some ideas of what to
look for. I believe the issue may be related to the type of DASD
being used.
Scenario, dd command to generate a 1G file if=/dev/zero takes 15s on
x86_64 platform. The same command takes 15m on the s390x platform.
In my environment the command takes 16s. My environment leverages
MOD-3 DASD while the environment in question has MOD-9 and MOD-27
devices. I know historically the MOD-9 is typically a slower device
but I don't know much about the MOD-27.
Is it truly possible that the performance of these devices is bad
enough to see such a difference between MOD-3 and x86_64 v. MOD-9 and
MOD-27? What else should / can I look at to determine the root cause
of the performance issues?
Hi Eric,
just for fun on our SLES10 s390x using 3390-9 (Shark) on a z/900 under
z/VM 5.2 without any tuning at all:
ihlscov2:~ # time dd bs=1024 count=1048576 if=/dev/zero of=/test1
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB) copied, 72.3474 seconds, 14.8 MB/s
real 1m12.357s
user 0m0.944s
sys 0m23.172s
ihlscov2:~ #
Mark
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