Sorry if this is the wrong contact to ask this
I am running RHEL 5.5 w/ device-mapper-multipath-0.4.7-34.el5
I am trying to tune my disks for better performance with the settings
echo 2048 > /sys/block/$bdev/queue/read_ahead_kb
echo 64 > /sys/block/$bdev/queue/nr_requests
echo deadline > /sys/block/$bdev/queue/scheduler
echo 8192 > /sys/block/$bdev/queue/max_sectors_kb
On the individual disk when I do this I get a big jump in read
performance of nearly 2x
# dd if=/dev/sdig bs=1024k of=/dev/null skip=3000 count=3000
3000+0 records in
3000+0 records out
3145728000 bytes (3.1 GB) copied, 13.8672 seconds, 227 MB/s
# dd if=/dev/sdig bs=1024k of=/dev/null skip=9000 count=3000
3000+0 records in
3000+0 records out
3145728000 bytes (3.1 GB) copied, 7.70806 seconds, 408 MB/s
So /dev/sdig is part of a multipath
# ls -l /sys/block/dm-119/slaves/
total 0
lrwxrwxrwx 1 root root 0 May 14 12:14 sdez -> ../../../block/sdez
lrwxrwxrwx 1 root root 0 May 14 12:14 sdif -> ../../../block/sdif
I apply the tuning to both sdez and sdif, however, when I do the
dd read test on the dm device, it is still slow
# dd if=/dev/dm-119 bs=1024k of=/dev/null skip=18000 count=3000
3000+0 records in
3000+0 records out
3145728000 bytes (3.1 GB) copied, 15.1546 seconds, 208 MB/s
Fine, I need to apply the tuning to the dm-119 device itself. But there
is no queue sub dir in /sys/block/dm-119
# ls /sys/block/dm-119
dev holders range removable size slaves stat subsystem uevent
So how do I tune the multipath device itself?
--
---------------------------------------------------------------
Paul Raines email: raines at nmr.mgh.harvard.edu
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging
149 (2301) 13th Street Charlestown, MA 02129 USA
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