>>>>> "Jens" == Jens Axboe <ax...@kernel.dk> writes:

>> I think we should fix sd.c to only send WRITE SAME if either of the
>> variants are explicitly listed as supported through REPORT SUPPORTED
>> OPERATION CODES, or maybe through a whitelist if there are important
>> enough devices.

Jens> Yep

I hate it too. But the reason it's assumed on is that there is
essentially no heuristic that works. Just like we assume that READ
always works.

Out of the ~200 devices I have access to in the lab:

 - 100% of the SAS/FC disk drives and SSDs support WRITE SAME
 - Only 2 out of about 50 different drive models support RSOC
 - About half of the arrays support WRITE SAME(10/16)
 - None of the arrays I have support RSOC

So even if we were to entertain using RSOC for "enterprise" transport
classes (which I concur would be nice for other reasons), it wouldn't
solve the WRITE SAME problem...

-- 
Martin K. Petersen      Oracle Linux Engineering

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