====== Using a SSD as Boot Device ======
If you are lucky enough to have a SSD drive available as boot device you'll certainly want to use it.\\
One important fact to know about SSDs is that you need to "clean" them on a regular basis to maintain top performances. This is done using the TRIM command:

TRIM allows the OS to "inform a solid-state drive (SSD) which blocks of data are no longer considered in use and can be wiped internally". Without using TRIM, the SSD speed decreases after a while so if you have a solid-state drive that supports TRIM, you should enable it so your SSD remains fast over time.

===== Determine if Your SSD supports TRIM =====
You first need to make sure that your SSD supports the TRIM command, to do that use the following commands:
<code>
sudo hdparm -I /dev/sda | grep "TRIM"
</code>

You might have to use another device identifier than// /dev/sda// for you it might be// /dev/sdb// or// /dev/sdc//. To get your disk identifier, use:
<code>
sudo fdisk -l
</code>


===== fstab or cron ? =====
==== Online discard in fstab ====
Although using online discard (in fstab) seems to be **NOT RECOMMENDED**, in case you really want to use this technique, open /etc/fstab as root with a text editor:
<code>
sudo nano /etc/fstab
</code>

And add the "discard" option (separated by a comma and no space!) to the SSD partitions you want to enable TRIM for. Here's an example:
<code>
<file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sdb1 during installation
UUID=1cd2fc4f-7d99-4c7a-8ea7-6f9a2d5e5960 /               ext4    discard,errors=remount-ro 0       1
</code>


==== Using a daily cron job ====
Using a timed cron job, the SSD trimming will occur on a regular basis you decide of (daily is probably a good choice). **This is the recommended way to TRIM your SSD**.

To use a daily cron job (so the trimming will occur once a day) for TRIM (fstrim), open /etc/cron.daily/trim as root with a text editor (/etc/cron.daily/trim doesn't exist so this will create the file):
<code>
sudo nano /etc/cron.daily/trim
</code>

and paste this:
<code>
#!/bin/sh
LOG=/var/log/trim.log
echo "*** $(date -R) ***" >> $LOG
fstrim -v / >> $LOG
fstrim -v /home >> $LOG
</code>

The last two commands in the code above perform the actual trimming for the root (/) and home (/home) partition and you need to edit them: here, add the SSD partitions for which you want to enable the daily TRIM job (usually, you must add "/" if the root partition is on the SSD and "/home" if you've set up a separate home partition).

Before saving the file, you can check if the fstrim command works:
<code>
sudo fstrim -v /
</code>

The output should look similar to this:
<code>
sudo fstrim -v /
/: 8158715904 bytes were trimmed
</code>

Once you've added your SSD partitions, save the file and make it executable using the following command:
<code>
sudo chmod +x /etc/cron.daily/trim
</code>

The system executes the daily cron (using anacron, even if your computer is turned off at that time, the job will still be performed later on) jobs at around 06:25 so each day after that time, you can check the /var/log/trim.log log file to see the fstrim output.

reference: [[http://www.webupd8.org/2013/01/enable-trim-on-ssd-solid-state-drives.html]]