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I have Ubuntu 12.04 running on my new server, and it is setup to run off of one drive, then 2 drives that are mirrored using mdadm. When streaming files or media from it, it is extremely slow. I was told that by default, mdadm uses 10% of my CPU for the array. So what I would like to know is, how can I increase the read speed of an array? I don't see options in /etc/mdadm/mdadm.conf, and Googling doesn't reveal anything

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The answer is in these two files:

  • /proc/sys/dev/raid/speed_limit_min
  • /proc/sys/dev/raid/speed_limit_max

These two files contain the minimum and maximum values of speed in kB/s.

Do something like this and maybe the repair speed will increase:

echo 200000 >  /proc/sys/dev/raid/speed_limit_min
echo 500000 >  /proc/sys/dev/raid/speed_limit_max

Source: http://en.wikipedia.org/wiki/Mdadm#Increasing_RAID_ReSync_Performance

Notes:

  • The /proc/mdstat file tells you about the current speed process
  • I know nothing about the -G option in the Wikipedia article
  • This actually did not help increasing the repair process speed on my own RAID array. It was stuck at around 130000K/sec.
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