Hi John- Sorry, I was out for a couple of weeks and have been catching up...
Re: sg support, there were issues in the past with people attempting to do SG_IO through dm-mp assuming that DM would handle retry on other paths, which it didn't. You also have to be aware that non-idempotent commands don't work right if retried. My recommendation would be to avoid implementing it, although there has been interest in a better way to do multipathed "generic" commands (e.g. virt pass-through) I think that is a more involved project than you want to do here. I see the discussion has progressed re: ALUA support in your later patch postings, which is good. As Hannes said, a Native SCSI MP would be useless without it. You don't have to support the older non-ALUA mechanisms though, those arrays are way, way old. SCSI does not have the equivalent of NVMe's AEN, so you need a way to ensure that your ALUA info is up-to-date. DM-MP's path checker normally does this by sending commands on which the Unit Attention can be reported so that the code can fetch up-to-date ALUA info. Hannes made some optimizations years ago to avoid excessive RTPG commands with large numbers of LUNs which we would need also. It will be necessary for the functionality to be enabled via a module option, at least initially. Introducing this in general use will be a big change for people who have Enterprise SAN configurations with their own custom path monitoring tools. I believe we put some functionality into usespace multipath tools so e.g. Native NVMe devices can still be monitored/observed which made things a bit easier for people. Unfortunately I will not be able to attend LSF/MM this year. I am sure it will be a good discussion. -Ewan On Wed, Feb 25, 2026 at 4:27 AM John Garry <[email protected]> wrote: > > On 25/02/2026 08:11, Hannes Reinecke wrote: > > And I _still_ want to have a blktests for persistent reservations ... > nvme/054 supports resv testing. > > For scsi PR, we could use util-linux, which has blkpr. > > >
