I have not blogged for a while, now that I am on summer holiday and got a new laptop I finally have something to blog about. I got a Thinkpad T430 and installed a Samsung SSD 830 myself. The 830 is not actually the best choice for a Linux user because you can only download firmware updates with a Windows tool. The tool does let you make a bootable FreeDOS USB disk with which you can apply the update, so you can use a Windows system to download the update and apply it just fine on a Linux system. The reason I got this SSD is that it is 7 mm in height and fits into the T430 without removing any spacers.
I installed Fedora 17 on the laptop and selected drive encryption in the Anaconda installer. I used ext4 and did not use LVM, I do not think it would be of much use on a laptop. After the installation I discovered that Fedora 17 does not enable SSD TRIM/discard automatically. That is probably a good default, apparently all SSDs do not support it. When you have ext4 partitions encrypted with LUKS as Anaconda does it, you need to change two files and regenerate your initramfs to enable TRIM.
First, edit your /etc/fstab and add discard to each ext4 mount. Here is an example of my root mount:
/dev/mapper/luks-secret-id-here / ext4 defaults,discard 1 1
Second, edit your /etc/crypttab and add allow-discards to each line to allow the dmcrypt layer to pass TRIM requests to the disk. Here is an example:
luks-secret-id-here UUID=uuid-here none allow-discards
You need at least dracut-018-78.git20120622.fc17 for this to work, which you should already have on an up-to-date Fedora 17.
Third, regenerate your initramfs by doing dracut -f. You may want to take a backup of the old initramfs file in /boot but then again, real hackers do not make backups 😉 .
Fourth, reboot and check with cryptsetup status luks-secret-id-here and mount that your file systems actually use discard now.