On 05/04/2012 09:57 AM, Albe Laurenz wrote: > Martin Grotzke wrote: >>> You could try different kernel I/O elevators and see if that >>> improves something. >>> >>> I have made good experiences with elevator=deadline and >>> elevator=noop. > >> Ok, great info. >> >> I'm not sure at which device to look honestly to check the current >> configuration. >> >> mount/fstab shows the device /dev/mapper/VG01-www for the relevant >> partition. When I check iostat high utilization is reported for >> the devices dm-4 and sda (showing nearly the same numbers for util >> always), >> so I suspect that dm-4 is mapped on sda. > > Use the option -N of "iostat" to see long device names. You can use > "lvm" to figure out the mapping. iostat with -N shows VG01-www for dm-4. For lvm/lvdisplay/dmsetup I get "Permission denied" as I have no root/sudo permissions. I need to check this with our hosting provider (hopefully we have a call today). >> This is the current config: $ cat /sys/block/sda/queue/scheduler >> noop anticipatory deadline [cfq] $ cat >> /sys/block/dm-4/queue/scheduler none > > Do you mean literal "none" or do you mean that the file is empty? "none" was the output of `cat /sys/block/dm-4/queue/scheduler`. >> Which of them should be changed? I'll discuss this also with our >> hosting provider next week, he'll know what has to be done. > > I'd just add "elevator=deadline" to the kernel line in > /etc/grub.conf and reboot. At least if it is a dedicated database > machine. > > But of course you want to change it on the fly first to test - not > knowing the answer to your question, I would change it in both > devices if I can. Ok, makes sense. Cheers, Martin
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