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Performance Note - Disabling Drive Command Queuing

Page history last edited by Redhat Virgil 10 years, 10 months ago

We were finding that using these NAS units showed some poor disk speed performance when we were running backups to the unit.  After some work on the unit, one of the guys (with a ton more linux knowledge than myself) found that disabling the command queuing helped.  His notes below:

 

If performance drops on the drive, and you ssh in and run "dmesg l more" and look for the following errors:
 
ata1.00: spurious completions during NCQ
ata1: soft resetting port

ata1.00: configured for UDMA/XXX

exception Emask 0x10 SAct 0x7 SErr 0x400100 action 0x2 frozen

 

 
To fix, do the following from an SSH session:
  1. Run "vi /etc/init.d/S99commandqueue"
  2. Insert the following into the file (type "i" to get into insert mode):

    #!/bin/sh

    echo 2 > /sys/block/sda/device/queue_depth

    echo 2 > /sys/block/sdb/device/queue_depth

    echo 2 > /sys/block/sdc/device/queue_depth

    echo 2 > /sys/block/sdd/device/queue_depth

  3. Save and quit (press "Esc" then ":wq")
  4. Run "chmod 755 /etc/init.d/S99commandqueue"
  5. Reboot the NAS

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