All, I don't think the kernel is yet tracking SSD vs Rotational. It would be a nice patch if someone would do that. I don't maintain the subsystem, but I assume it would be accepted if well done. You could model your patch by looking at how the drive topology patches were done. Effectively this patch would do the same thing. (Petersen wrote those, so I think these are them: http://markmail.org/message/azj3z4tofrknnbbe) My thoughts: ===> How to tell For SATA: Per T13/1699-D Revision 4a (from May 2007) word 217 of the identify block should be populated with a "1" to identify non-rotating media. http://www.t13.org/Documents/UploadedDocuments/docs2007/D1699r4a-ATA8-ACS.pd... IIRC: The identify block is read during drive query time, so you should not have to actually generate any i/o. Just patch the portion of the kernel working with the identify block. ie. See the topology patch. For SCSI - no idea, but I'd be surprised if they did not already have a scsi flag for it. The topology patch also handled SCSI, so it's just a matter of finding the scsi field to use. ===> Quirks Lots of manufacturers don't follow the specs on something like this, so a quirks functionality is typically how the ATA driver handles it. ie. If you find a SSD that is not setting the flag, then setup a quirk to override the flag. The quirk table should be based on make & model at a minimum, and maybe firmware. You should be able to find existing quirk logic, so don't invent your own. SCSI seems to be followed much more accurately, so you may not need a quirks functionality for it. ===> userspace API Seems like there should be a "/sys/block/sda/*" file that allows userspace to interrogate. The topology patches added a few of these, so one more would be good. If you can generate the same data for scsi, maybe just create /sys/block/sda/rotation_speed and have it just reflect exactly word 217 of the identify block. Greg