On 11-10-03 04:25 PM, Alan Stern wrote:
On Mon, 3 Oct 2011, Amit Sahrawat wrote:
Hi,
Please find the USB Analyzer - logs for '6' USB based Mass Storage
devices attached.
Too bad the analyzer log presents only the response, not the command.
So, only for one of the USB HDD(Seagate - Free Agent), the response
obtained is correct.
I don't understand the format of the Seagate Free Agent MODE SENSE
data. Maybe someone else can interpret it; here it is for reference:
SCSI Op(3) ADDR(4) Tag(0x00000004) SCSI CDB MODE SENSE(6)
_______| Data(
__ 000: 1C 00 00 00 86 0B 00 02 00 00 12 A1 9E B0 3C 01 00 1A 0A 00 01 00 00 00 00 00 00 0B B8 00 00 00
__ 032: 00 00 00 00 1A 0A 00 01 00 00 00 00 00 00 0B B8 A2 06 00 00 00 00 00 00 78 20 55 53 42 32 2E 30
__ 064: 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 7F FF 00 00 00 00 80 FA 0B C2 50 21 4E 41 30 42
__ 096: 36 58 33 4C 00 30 00 00 00 32 43 46 45 39 42 00 70 F5 12 00 74 FF 00 00 00 00 00 00 00 00 00 00
__ 128: 3C 00 00 0B B8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 02 50 01
__ 160: 46 72 65 65 41 67 65 6E 74 20 47 6F 46 6C 65 78 10 50 11 46 72 65 65 41 67 65 6E 74 20 47 6F 46)
The RBC device parameters mode page followed by a Power
Condition mode page. The RBC device parameters mode page
is the only SCSI page I have seen (mode, log, VPD, etc)
with a 5 byte field!
Decoded response to a probable MODE SENSE(6) "fetch all
pages" command:
RBC device parameters mpage:
WCD=0 [double negative: write cache enabled]
Logical block size: 512 bytes
Number of logical blocks: 0x12A19EB0 *** [160 GB]
Power/performance: 0x3c
READD: 0 [READ enabled]
WRITED: 0 [WRITE enabled]
FORMATD: 0 [FORMAT UNIT enabled]
LOCKD: 1 [media cannot be locked]
Power Condition mpage:
IDLE=0
STANDBY=1
IDLE_CONDITION_TIMER=0
STANDBY_CONDITION_TIMER=0xbb8 [300 seconds]
References: rbc-r10a.pdf [1999] + spc3r26 [2005]
Hopefully Seagate will switch to UAS(P) in the near future.
*** That is _not_ the address of the last valid LB as in
the SCSI READ CAPACITY command!
For the other devices this seems clear enough. In most of the cases,
the data doesn't include the Caching page. The Samsung and Transcend
devices _do_ provide their Caching pages, and in both of them the data
says that write caching is disabled. (In the Samsung case this is
wrong undoubtedly because of the JMicron bridge -- JMicron's firmware
is notoriously buggy.)
If you can suggest a robust way of determining whether or not a drive
supports SAT (one which won't cause non-supporting devices to crash),
it could be added. In the meantime, I'm not sure what else we can do.
Would it make sense to assume write caching is present and enabled if
the drive does not provide a Caching page?
No. You need to also take into account the RBC
device parameters mode page if present. See above.
Doug Gilbert
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