SSDs (solid state drives) are great. They’re shock resistant, consume less power, produce less heat, and have very fast seek times. If you have a computer with an SSD, such as an Eee PC, there are some tweaks you can make to increase performance and extend the life of the disk.

  1. The simplest tweak is to mount volumes using the noatime option. By default Linux will write the last accessed time attribute to files. This can reduce the life of your SSD by causing a lot of writes. The noatime mount option turns this off.

    Open your fstab file:
    sudo gedit /etc/fstab

    Ubuntu uses the relatime option by default. For your SSD partitions (formatted as ext3), replace relatime with noatime in fstab. Reboot for the changes to take effect.

  2. Using a ramdisk instead of the SSD to store temporary files will speed things up, but will cost you a few megabytes of RAM.

    Open your fstab file:
    sudo gedit /etc/fstab

    Add this line to fstab to mount /tmp (temporary files) as tmpfs (temporary file system):
    tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0

    Reboot for the changes to take effect. Running df, you should see a new line with /tmp mounted on tmpfs:
    tmpfs 513472 30320 483152 6% /tmp

  3. Firefox puts its cache in your home partition. By moving this cache in RAM you can speed up Firefox and reduce disk writes. Complete the previous tweak to mount /tmp in RAM, and you can put the cache there as well.

    Open about:config in Firefox. Right click in an open area and create a new string value called browser.cache.disk.parent_directory. Set the value to /tmp.

  4. An I/O scheduler decides which applications get to write to the disk when. Because SSDs are so different than a spinning hard drive, not all I/O schedulers work well with SSDs.

    The default I/O scheduler in Linux is cfq, completely fair queuing. cfq is works well on hard disks, but I’ve found it to cause problems on my Eee PC’s SSD. While writing a large file to disk, any other application which tries to write hang until the other write finishes.

    The I/O scheduler can be changed on a per-drive basis without rebooting. Run this command to get the current scheduler for a disk and the alternative options:
    cat /sys/block/sda/queue/scheduler

    You’ll probably have four options, the one in brackets is currently being used by the disk specified in the previous command:
    noop anticipatory deadline [cfq]

    Two of these are better suited to SSD drives: noop and deadline. Using one of these in the same situation, the application will still hang but only for a few seconds instead of until the disk is free again. Not great, but much better than cfq.

    Here’s how to change the I/O scheduler of a disk to deadline:
    echo deadline > /sys/block/sda/queue/scheduler

    (Note: the above command needs to be run as root, but sudo does not work with it on my system. Run sudo -i if you have a problem to get a root prompt.)

    You can replace sda with the disk you want to change, and deadline with any of the available schedulers. This change is temporary and will be reset when you reboot.

    If you’re using the deadline scheduler, there’s another option you can change for the SSD. This command is also temporary and also is a per-disk option:
    echo 1 > /sys/block/sda/queue/iosched/fifo_batch

    You can apply the scheduler you want to all your drives by adding a boot parameter in GRUB. The menu.lst file is regenerated whenever the kernel is updated, which would wipe out your change. Instead of this way, I added commands to rc.local to do the same thing.

    Open rc.local:
    sudo gedit /etc/rc.local

    Put any lines you add before the exit 0. I added six lines for my Eee PC, three to change sda (small SSD), sdb (large SSD), and sdc (SD card) to deadline, and three to get the fifo_batch option on each:
    echo deadline > /sys/block/sda/queue/scheduler
    echo deadline > /sys/block/sdb/queue/scheduler
    echo deadline > /sys/block/sdc/queue/scheduler
    echo 1 > /sys/block/sda/queue/iosched/fifo_batch
    echo 1 > /sys/block/sdb/queue/iosched/fifo_batch
    echo 1 > /sys/block/sdc/queue/iosched/fifo_batch

    Reboot to run the new rc.local file.

    [update] Commenter dondad has pointed out that it’s possible to add boot parameters to menu.lst that won’t be wiped out by an upgrade. Open menu.lst (Remember to make a backup of this file before you edit it):
    sudo gedit /boot/grub/menu.lst

    The kopt line gives the default parameters to boot Linux with. Mine looks like this:
    # kopt=root=UUID=6722605f-677c-4d22-b9ea-e1fb0c7470ee ro

    Don’t uncomment this line. Just add any extra parameters you would like. To change the I/O scheduler, use the elevator option:
    elevator=deadline

    Append that to the end of the kopt line. Save and close menu.lst. Then you need to run update-grub to apply your change to the whole menu:
    sudo update-grub[end update]

Want to know how fast your SSD or other storage device is? Using hdparm you can test the read performance of your disk:
sudo hdparm -t /dev/sda

The 4 GB SSD on my Eee PC 901 gets about 33 MB/s. My desktop PC’s hard drive gets about 78 MB/s. (What hdparm doesn’t show is that the seek time for an SSD is much, much lower than a hard disk.)

Have any other suggestions for SSDs, or disagree with any of these? Leave a comment to let me know.


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