Re: Samsung t5 / t3 problem with ncq trim

["Martin K. Petersen" <martin.petersen@oracle.com>]

Sven,

> The 850 had a problem with ncq trim, disks randomly died and got slow
> af with linux.

The NCQ quirk does not apply in your case since the drive is attached to
Linux via UAS. The UAS-SATA bridge drive may or may not be using NCQ
when talking to the drive; we have no way of knowing or influencing that
decision, that's all internal to the drive. We only see what is
presented on its external USB interface.

I don't have a T5 so I don't know about that. But I do have a T3 and it
does not report LBPME which is the SCSI way of saying the drive supports
TRIM. So Linux isn't even going to attempt to TRIM the drive in this
configuration.

You are welcome to send the output of the following commands:

# sg_inq /dev/sdN

# sg_readcap -l /dev/sdN

# sg_vpd -p bl /dev/sdN

# sg_vpd -p lbpv /dev/sdN

for your T5 so we can see what it reports. But with respect to the
queued TRIM issue, there isn't really anything that can be done from the
Linux side since this is all internal to the device.

Had the mSATA drive been directly attached to a SATA controller and not
a UAS-to-SATA bridge things would have been different. The special
handling of the 850 in libata is meant to address the scenario where
Linux is talking to the SATA drive directly. In that configuration the
decision about whether to queue or not queue the DSM TRIM operation lies
with Linux.

-- 
Martin K. Petersen	Oracle Linux Engineering