Changing disk schedule to noop in F16

[rehcla]

Hi all!

I try to setup my SSD Drive and followed the new "SSD Guide" in this forum:

Eliminate "Elevator" disk scheduler. [PERFORMANCE, RELIABILITY]

Rotating disks use the 'elevator' algorithm to schedule block access. This algorithm makes no sense for a SSD media where there are no cylinders and seek time is nearly constant.

Individual drives can use distinct scheduling algorithms by adding the following line to /etc/rc.d/rc.local
echo noop > /sys/block/sda/queue/scheduler

My problem is, that I cant find the file /etc/rc.d/rc.local on my Fedora 16 system!
Until now, I was editing /etc/sysctl.conf and adding a line;

block.sdb.queue.scheduler = noop

but that is not advised anymore!

Can someone point me in the right direction here?

Greetings

[stevea]

No - that won't work. Never did.
The sysctl.conf file manipulates the pseudo filesystem under /proc/sys NOT /sys

My problem is, that I cant find the file /etc/rc.d/rc.local on my Fedora 16 system!

Just create the file as an executable bash script owned by root.

[rehcla]

Hi Stevea!

Thanks for the quick reply!

Ho do I do that?
Just create the /etc/rc.d/rc.local file and make it executable via chmod?

Thanks

[DBelton]

would adding the kernel parameter elevator=noop do the same thing without having to go about all of the script stuff?

Edit:

Forget that. You can't set it for just one drive using the kernel parameter. It would set it for all drives.

and you are correct..

Just create the create the /etc/rc.d/rc.local file and make it executable via chmod.

If systemd doesn't automatically pick it up once it is created and set executable, the try enabling the rc-local.service.

systemctl enable rc-local.service

[Gareth Jones]

I suspect that the preferred method these days would be to add a udev rule rather than use rc.local. At a guess something like

ACTION=="add", KERNEL=="sda", RUN+="echo noop > /sys/block/sda/queue/scheduler"

in e.g. /etc/udev/rules.d/50-ssd.rules, but I don't know if that's quite correct. Also, there may be a more general way of detecting whether a device is solid-state or rotating (although if there was I'd assume udisks would already do so, so maybe not).