I am trying to understand how IO ordering safety is enforced with on path failover. This is new territory for me so forgive me if this is obvious. Consider the sequence: 1. client writes(lba=0,val=x) on path A. 2. multipath declares path A dead and retries write on path B 3. retried write on path B completes successfully and client get ack'd 4. client writes(lba=0,val=y) on path B. It also completes successfully and is ack'd to client 5. write from (1) completes and corrupts data It seems like multipath needs a guarantee at step 2 that the original write won't complete after path A has been declared down. I thought it would issue something like a LUN RESET on path B and that the response to that reset would indicate that it is safe to proceed. This page sort of supports that speculation: http://scst.sourceforge.net/mc_s.html In testing with dm-multipath accessing an LIO/IBLOCK device over FC, I don't see a LUN RESET. I also don't see any indication of this in the code but I might be missing something. It occurred to me that my target might not be setting the correct bits for multipathing. Any advice? -- Bob Bawn -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
