Quote Originally Posted by sreej1989 View Post
A simple fstrim on a thin-provisioned drive is returning "Not Supported" error on my machine SLES12 SP2. The drive in question supports SCSI UNMAP requests but the kernel logs reveal that it is actually sending WRITE_SAME(16) instead. Is this configurable by any means? I tried XFS and ext3. A lot of online documentation states that it is supposed to send UNMAP request. I'm trying to trace the request to understand more but any help would be appreciated!
I see that no one has provided a solution. I'm sorry I don't have one either but I have found some information that may help.

The man page says:
fstrim is used on a mounted filesystem to discard (or "trim") blocks which are not in use by the filesystem. This is useful for solid-state drives (SSDs) and thinly-provisioned storage.
You say:
A simple fstrim on a thin-provisioned drive is returning "Not Supported"
I suspect the manner in which blocks are trimmed may differ depending upon whether the object is an SSD or thinly-provisioned storage. Is sdb an SSD?

I found a few articles that may shed some light:

How, or even whether TRIM is supported, depends on the drive, the interface, motherboard chipset, file system, and perhaps other factors.

I hope you find the answers you are looking for.