Nearly three years ago, I wrote an article on optimizing for SSDs under Linux. Recently, I decided to revisit the issue after reading a recent blog post.
The recommendation at the time was to enable TRIM support, using the discard option to mount the drive. The first question is, if this is such a good idea, why isn’t it enabled by default? Why do you have to add it to your options, like below?
/dev/sda1 / ext4 discard,defaults
It turns out that enabling the discard option does have a performance hit on deletes. So, how do you keep your SSD Trimmed and avoid a costly performance penalty?
It turns out you can trim manually using the fstrim command, and set up a cron job to run this command once a day. The command takes only one argument by default, the mountpoint of the partition.
Seems like something worth thinking about. However, with the majority of the systems I run SSDs on, the solid state acts an an OS drive. Therefore, the number of deletes are minimal compared to writes.
In the end, enabling TRIM on your drive ensures that the drive will have the best wear-leveling and performance, but there is a cost. For some systems, it is just easier to mount with the discard option, others to run fstrim.
Related articles
Impact of “discard” mount option on Intel 525 SSD(kparal.wordpress.com)
Solid State Drives(wiki.archlinux.org)
Linux 3.9 brings SSD caching and drivers to support modern PCs(arstechnica.com)
