Enable noop scheduler by default for an SSD

[Blazeix]

As this thread is one of the top results for "ssd scheduler" I figured I'd add a bit of info to this thread. There is a small difference between the method where you modify menu.lst and the method where you modify sysfs.conf. The menu.lst method sets it for all drives, and the sysfs method changes it only for the drives you specify. For example the line

block/sda/queue/scheduler = noop

only changes the scheduler for the drive "sda". The two methods do the same thing only if you have one drive. If you have a mix of actual hard drives and SSDs, you'll want to use the sysfs method to enable it only on the SSDs. If you only have SSDs, it's easiest to use the menu.lst method.

[chmac]

Thanks Blazeix, I've just updated to the sysfs.conf method. I occassionally plug in USB spinning disks, so I think it makes sense to set the noop schedulere just for sda.

[Captain_Bodge]

Does it make any difference? Have you compared performance with noop to performance with cfq? I've read some conflicting results.

[chmac]

To be honest, I haven't noticed any performance difference, but I haven't run any tests. I think there's a chance it puts slightly less wear on the drive, so I'm happy to switch for that reason. My laptop is usually under fairly low load so I don't really notice disk performance.

[magicfab]

I've summarized current information about SSD configuration in Ubuntu 10.10, including the information in this thread, here:

https://wiki.ubuntu.com/MagicFab/SSDchecklist

Thanks for any comments/suggestions.

[csarlee]

@MagicFab

Thanks for the link, it is awfully complete and good guide!!!

[Skip Da Shu]

This might make you rethink using "noop"... the other good ssd option is "deadline".

noop vs deadline


My Mushkin 40GB SSD in my Lenovo netbook with "EXT4, noatime, discard and /tmp mounted to tmpfs" gives me:

Using "deadline" -
buffered 548MB in 3.01 = 182.71 MB/sec
cached 1518MB in 2.00 = 759.52 MB/sec

Using "noop" -
buffered 552MB in 3.01 = 183.14 MB/sec
cached 1492MB in 2.00 = 746.73 MB/sec

Not much of a difference either way. A <1MB buffered adv to noop and 13MB cached adv to deadline. What does a netbook do more of "buffered" or "cached" reading? Not sure I really know the diff. So for now I'm leaving it on deadline which is what it's been since the install of the SSD.


I'll be replacing my SATA-I 74GB 10K WD boot drive next week with an OCZ Vertex 2 64MB so I'll have to run these on that and see the diff.