Hello listers, We've hit a pretty nasty bug in SLES 11 SP2 kernel at 3.0.34 and higher. Basically the I/O goes crazy - like 4000-6000 i/o per sec - and the server becomes unresponsive. It's highly creatable by running a WebSphere deploy or starting WMB sw. SuSE says there is a bug in cfq and the work around for now is to set elevator=deadline in the kernel parameters. This does seem to mitigate the problem.
It's got me wondering though what is the current recommendation is for z on ECKD DS8700. This doc http://doc.opensuse.org/products/draft/SLES/SLES-tuning_sd_draft/cha.tuning.io.html says "On IBM System z the default I/O scheduler for a storage device is set by the device driver", but trying to query what it is seems to indicate that everything is deadline already (but it must not be or the parm wouldn't have helped). Trying to query with cat /sys/block/dasd*/queue/scheduler comes back always with [deadline] being the default, even if elevator= isn't specified in the parms. Is there another way to query it? This IBM presentation seems to indicate that deadline is the default on z (but maybe it's not now as of kernel 3.0.34?) http://people.redhat.com/bhinson/pdfs/BestPractices_IBM.pdf And some older doc seems to indicate that noop is the best choice with intelligent disk subsystems like DS8xxx. Any insight would be most helpful! Marcy This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
