elevator=deadline
29937 0 -rw-r--r-- 1 root root 4096 Mar 7 16:27 ./devices/virtual/block/VxVM3000/queue/scheduler
30024 0 -rw-r--r-- 1 root root 4096 Mar 7 16:27 ./devices/virtual/block/VxVM4000/queue/scheduler
30128 0 -rw-r--r-- 1 root root 4096 Mar 7 16:27 ./devices/virtual/block/VxVM4001/queue/scheduler
31259 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP2/queue/scheduler
31642 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP3/queue/scheduler
31780 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP4/queue/scheduler
31918 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP5/queue/scheduler
32056 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP6/queue/scheduler
32194 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP7/queue/scheduler
32301 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP8/queue/scheduler
32439 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP9/queue/scheduler
32546 0 -rw-r--r-- 1 root root 4096 Mar 5 11:51 ./devices/virtual/block/VxDMP10/queue/scheduler
21089 0 -rw-r--r-- 1 root root 4096 Mar 7 16:27 ./devices/pci0000:00/0000:00:09.0/0000:09:00.0/host0/rport-0:0-2/target0:0:0/0:0:0:0/block/sda/queue/scheduler
20640 0 -rw-r--r-- 1 root root 4096 Mar 7 16:27 ./devices/pci0000:00/0000:00:09.0/0000:09:00.0/host0/rport-0:0-2/target0:0:0/0:0:0:1/block/sdb/queue/
chrbl357:/sys # cat ./devices/virtual/block/VxVM3000/queue/scheduler
[noop] deadline cfq
chrbl357:/sys # cat ./devices/virtual/block/VxVM4000/queue/scheduler
[noop] deadline cfq
chrbl357:/sys # cat ./devices/virtual/block/VxDMP2/queue/scheduler
none
chrbl357:/sys # cat ./devices/virtual/block/VxDMP7/queue/scheduler
none
chrbl357:/sys # cat ./devices/pci0000:00/0000:00:09.0/0000:09:00.0/host0/rport-0:0-2/target0:0:0/0:0:0:0/block/sda/queue/scheduler
[noop] deadline cfq
chrbl357:/sys #
We change the scheduler option down the "/sys/block" path. In this instance we change it to noop but more often it is changed to deadline. However am confused about the scheduler file under VxVM3000 or VxDMPx. How does this interact with the block device scheduler settings?
Hi Charl,
VxVM is hard coded to use the deadline scheduler for VxVM#### volume devices. If you specify a different scheduler in your grub.cfg, it still won't change on the VxVM volume devices.
The only way to get it to change is to modify the /sys/block device, which it looks like you have already done. However, this only works temporarily. Once you reimport the DG it will go back to deadline.
Because the VxVM volume is not a physical device, changing the scheduler should not have a very big impact on performance. The IO sent to the VxVM volume device is passed down to the underlying physical devices which should be using whatever scheduler was specified in grub.
Bottom line is that there is no easy way to permenantly change the scheduler for VxVM volume devices. The scheduler for the underlying physical device is what really matters.
Best Regards,
Max
