Playing around with using a modern kernel (2.6.37 currently) on an older OS (CentOS 5.5) so we can get TRIM (discard) working on our SSDs (Crucial C300s).
The most recent hdparm (9.37) concurs that the C300 supports TRIM:
./hdparm -I /dev/sdc | grep TRIM * Data Set Management TRIM supported (limit unknown) * Deterministic read data after TRIM
But the kernel doesn't seem to agree when I attempt to mount /dev/sdc with the discard option:
EXT4-fs warning (device sdc): ext4_issue_discard:2619: discard not supported, disabling
We're experimenting with other Linux flavors as I type this, but it'd be nice to know what's going on, regardless.
Is this a manifestation of some other ancient component of CentOS 5.5 that's misinforming the kernel? Or maybe is hdparm using a different mechanism than the kernel to determine whether TRIM is supported?