I don't understand - where would an installation with many linux servers get
SCSI I/O
information that identifies a device response time and shows delays associated
with that
I/O? I/O statistics are "nice", but how are they helpful?
Ingo Adlung wrote:
That's somewhat outdated information at least for SLES 9 & 10.
We have Linux I/O statistics for FCP/SCSI and shortly we'll have
FCP adapter I/O statistics, too.
It is true that ECKD attached disks provide QoS features like
end-to-end data protection and is the dominant I/O attachment
for Linux. It is also true that customers would usually observe
higher throughput with FCP attached storage.
More performance related data to disk I/O is available at
http://www-128.ibm.com/developerworks/linux/linux390/perf/index.html
and more specific information for related to the DS8000 at
http://www-128.ibm.com/developerworks/linux/linux390/perf/tuning_res_dasd_ds8000.html
Best regards
Ingo
Linux on 390 Port <[email protected]> wrote on 26.03.2007 22:38:21:
When performance is bad, do you want to know why? Until we know how
to show when the SAN
is impacting your application and how - do you want to trust your
production to something
where performance is not manageable?
For example, an ibm controller was benchmarked first as eckd, then
as scsi. on eckd, we
get cache stats - could show the dasd fast write filled up, and
could show response time.
for scsi, all we could show was thruput was degraded. we can't
even measure silly
response time numbers on scsi.
Lionel B. Dyck wrote:
I've heard several good reasons to have my zlinux images use dasd that is
on the fibre connected san and a few for using the old tried and true
dasd. What I'd like to find out is what is true and what isn't - basically
what is considered the best practice for zlinux dasd.
Thus - what do y'all think?
Thanks in advance.
Lionel B. Dyck, Consultant/Specialist zLinux Platform
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note:If you can't measure it, I'm just not interested
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