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I have an SSD main disk and I want to use noop IO scheduler with it, like this:

echo noop > /sys/block/sda/queue/scheduler

But this setting gets lost after reboot. What is a right place to save this setting in Fedora 18? Or, may be, on linux in general?

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up vote 2 down vote accepted

The best way to do this is with a udev rule. Add a file to /etc/udev/rules.d with a rule that looks something like this:

ACTION=="add", SUBSYSTEM=="block", ENV{ID_BUS}=="scsi", ENV{ID_SERIAL}=="xxx", ATTR{queue/scheduler}="noop"

Obviously you should replace xxx with the correct serial number for the disk in question. You can find that, and other attributes you could match on, with:

udevadm info --path=/sys/block/sda --query=property

The advantage of using udev to do this, and matching on attributes like the disk serial number, is that it won't matter if it doesn't always appear at sda.

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Additions to an answer: ENV{ID_BUS} is also customizable and should be "yyy"; when naming the rule file, try udevadm test /sys/block/sda to be sure that your rule is applied after all others. – abyss.7 Jan 28 '13 at 7:11

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