Hello, all. Sorry to trouble the list but I have been googling and reading for the better part of two days. How does one control path priorities in dm-multipath? For example, in our test environment in which we are attempting to learn dm-multipath, we have a Nexenta opensolaris based iSCSI SAN with ten Ethernet ports on the SAN network divided equally between two GbE switches. We have a Linux server with four Ethernet ports on the SAN. opensolaris only supports 802.3ad for port bonding which required us to plug all bonded ports into the same switch. That was an unacceptable single point of failure for us so we decided to explore dm-multipath for fault tolerance. To optimize network throughput, we decided to divide the storage pool for the server into four LUNs - one per server interface to the SAN network (the SAN network is subnetted to provide a unique subnet for each SAN interface). We then thought we would implement RAID0 across the four LUNs to stripe across all interfaces simultaneously. We assumed this would give us better performance than dm-multipath's multibus with round robin. However, we would prefer the traffic stay within the same switch and not needlessly traverse the switch trunks. Thus, we really want to lock a port on the Server to a LUN and use the SAN interface which is on the same switch as the Server interface. We also want each Server interface to be able to access each SAN LUN through either of two interfaces on the SAN. The idea is we can thus tolerate a failure of any one switch and literally all interfaces but one on either the SAN or Server. This yields 32 SCSI devices (4 interfaces connected via two paths to four LUNs = 4 * 2 * 4). Again, we want to lock one interface per LUN as the top priority interface to ensure we are striping across all interfaces and we are not crossing switches except in failover mode. The second priority interface should be a different Server interface on the same switch. The third priority should be a different Server interface on a different switch. How does one prioritize paths in dm-multipath? I even tried creating a prio_callout script which did nothing but capture any passed parameters (so I could try to write a custom handler based upon what was passed into the script) but the call does not appear to pass in any parameters. HELP? Thanks - John -- John A. Sullivan III Open Source Development Corporation +1 207-985-7880 jsullivan@xxxxxxxxxxxxxxxxxxx http://www.spiritualoutreach.com Making Christianity intelligible to secular society -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
