On Mon, 2017-09-25 at 21:46 -0400, Martin K. Petersen wrote: > Ewan, > > > Some devices do not support a WRITE SAME / WRITE SAME(16) with the > > UNMAP bit set up to the length specified in the MAXIMUM WRITE SAME > > LENGTH field in the block limits VPD page (or, the field is zero, > > indicating there is no limit). Limit the length by the MAXIMUM UNMAP > > LBA COUNT value. Otherwise the command might be rejected. > > From SBC4: > > "A MAXIMUM UNMAP LBA COUNT field set to a non-zero value indicates the > maximum number of LBAs that may be unmapped by an UNMAP command" > > Note that it explicitly states "UNMAP command" and not "unmap > operation". > > "A MAXIMUM WRITE SAME LENGTH field set to a non-zero value indicates > the maximum number of contiguous logical blocks that the device server > allows to be unmapped or written in a single WRITE SAME command." > > It says "unmapped or written" and "WRITE SAME command". > > The spec is crystal clear. The device needs to be fixed. We can > blacklist older firmware revs. > Yes, I know that is what SBC-4 says, and I agree that the devices are not conforming. Unfortunately, I've come across 3 different arrays now from 3 different manufacturers that exhibit this behavior. cc: Fred Knight for his opinion on this (NetApp was not one of the arrays that I've run into, though). -Ewan
