How to enable TRIM?

Question

I know that the Linux kernel supports TRIM as of version 2.6.33, so there should be TRIM support in ubuntu 10.10.

Is TRIM enabled by default or do I need to change some settings or install additional software for it to work? If so, how?

Answer 1

There are two forms of TRIM, manual (wiper.sh) and automatic:

1) Manual TRIM

In ubuntu this can be performed with wiper.sh, but is not needed when automatic TRIM is enabled.

2) Automatic TRIM

Automatic TRIM is supported since kernel 2.6.33 with the EXT4 file system

For automatic TRIM to work, the drive needs to be mounted with the "discard" option in fstab. To add this option run:

sudo cp /etc/fstab ~/fstab-backup
gksudo gedit /etc/fstab

add discard to options on the entry for the SSD; the line should read similar to this:

UUID=ed586ab8-08c5-4bae-b118-d191b716b4a4 /               ext4    discard,errors=remount-ro 0       1

reboot, automatic TRIM should now be working.

Testing automatic TRIM:

To Test if Trim is working issue the following commands (adapted from here):

cd  / #or whatever part of the file system is on the SSD
sudo dd if=/dev/urandom of=tempfile count=100 bs=512k oflag=direct # you will not need sudo for these to work, if your SSD is in /home for example
sudo hdparm --fibmap tempfile    

From the output copy the number under "begin_LBA" and use it in the next command. Also check the system name of your SSD: System->Administration->Disk Utility (sda, sdb, or sdc ...)

sudo hdparm --read-sector 2638848 /dev/sda #replace 2638848 with the number obtained before and /sda with your SSD drive

you should receive a a long string of characters for those sectors

sudo rm tempfile
sync
sudo hdparm --read-sector 2638848 /dev/sda

even after removing the file the sectors are still not empty. Wait a while then run the command again

sudo hdparm --read-sector 2638848 /dev/sda

if you get only zeros, then automatic TRIM is working.