On Sat, Dec 15, 2012 at 5:23 PM, Russell Coker
[off-list ref] wrote:

I've got a system running Debian kernel 3.2.0-4-amd64 with root on a SSD that
identifies itself as "INTEL SSDSC2CT12 300i" (it's an Intel 120G device).

3.2 is massively old in btrfs terms, with lots of fun little stability
and performance bugs.

Here is the /proc/mounts entry which shows that ssd and discard options are
enabled.

/dev/disk/by-uuid/7939c405-c656-4e85-a6a0-29f17be09585 / btrfs
rw,seclabel,nodev,noatime,ssd,discard,space_cache 0 0

Don't use discard; it's a non-queuing command, which means your
performance will suck unless your device is _really_ terrible at
garbage collection (in which case, it's just the lesser of two evils).