On Thu, Mar 15, 2018 at 12:19:11PM +0100, Douglas Gilbert wrote: > On 2018-03-15 10:47 AM, Kashyap Chamarthy wrote: > > On Wed, Mar 14, 2018 at 11:43:55PM -0400, Martin K. Petersen wrote: > > > > > > Kashyap, > > > > Hi Martin, > > > > > > Sorry, I didn't give you complete information — with the previous > > > > `dmesg` output, I actually attached the SSD (Samsung T5) via regular USB > > > > "A Cable". > > > > > > > > Now, I re-attached the SSD via the "Thunderbolt" port on my other laptop > > > > (Lenovo T470s), it _does_ show "UAS". Refer the arrow below: > > > > > > Do you get different sg_readcap -l output when accessing it in UAS mode? > > > I.e. is lbpme=1? > > > > Afraid, no :-( I was excited for a brief moment, but it's the same as > > earlier. The result with the SSD via 'Thunderbolt': > > > > $> sudo sg_readcap -l /dev/sdc > > Read Capacity results: > > Protection: prot_en=0, p_type=0, p_i_exponent=0 > > Logical block provisioning: lbpme=0, lbprz=0 > > Last logical block address=976773167 (0x3a38602f), Number of logical blocks=976773168 > > Logical block length=512 bytes > > Logical blocks per physical block exponent=0 > > Lowest aligned logical block address=0 > > Hence: > > Device size: 500107862016 bytes, 476940.0 MiB, 500.11 GB > > > > > > /me naively wonders if it has anything to do with accessing it via > > Linux. > > You can also run 'sg_readcap -l' on a Windows machine to test your theory. > Do 'sg_scan.exe' first to see where (and if) the 'physical disk' is, then > you would do something like: > sg_readcap -l pd2 > > There is no IOS port of sg3_utils. > > I am not aware of any SCSI command *** (and haven't seen any ATA or NVMe > commands) that tell a storage device something like: "BTW I'm a Linux > machine running Ubuntu 17.10 on xxxx hardware". > > It is possible that a storage device might recognize an OS by the pattern > of commands it sends, especially in the device discovery mode. > > So basically your suggestion is a long shot. There might be a "secret" > setting in a vendor specific command that another OS is aware of. > For example, according to the 'net this command: > sg_raw /dev/sr0 EA 00 00 00 00 00 01 > allows owners of Apple USB Superdrives to use them on other OSes. I see, thanks for the explanation and the specific useful commands. I'll try to get hold of a friend's Windows computer, as I don't have one with me. But your "long shot" comment adjusted my expectations to not hold my breath. > *** there are transport_ids used by PERSISTENT RESERVATION commands to > differentiate one machine from another. But they convey about as > much information as a random number does. Also that applies to a > multi-initiator, single target model which isn't the case when we > are talking about USB/Thunderbolt attachment. > -- /kashyap
