I have set up LVM to cache a logical volume (located on an HDD) on a partition of an SSD (in writeback mode if this matters). As far as I can tell, this works correctly and the cache uses all available space.
Now, I am wondering whether this setup issues TRIM command to the SSD and whether issuing such commands is necessary (or reasonable) to extend the SSD's lifetime. I have added
discard to the options in
/etc/fstab for the cached logical volume's entry. However, I have no idea how this affects the cache partition nor do I have an idea on how to test whether TRIM commands are issued.