Le vendredi 17 d?embre 2004 �7:19 +0000, Arthur Bergman a �it : > Hi, > > I got dm-multipath working using multibus and roundrobin against a IBM > SVC (San Volume Controller) backed SAN. This is instead of using the > IBM supplied SDD that only works under 2.4. The SVC is fronting for a > number of different IBM/LSILogic RAID controllers. Everything is > working fine and failover works (takes 30 seconds but I haven't tried > to actually bring tweak the QLA setting so I expect that to go down). > Yes, testers report good behaviour with qlport_down_retry=1 > The SVC is actually two linux boxes with 4 FC ports each, all ports in > the cluster are active and there is no fail over cost for using paths > against different nodes in the cluster, we managed to see over 200 > MB/sec sequential write speeds against it, this is inline with expected > performance. However the read speed is much slower than on SDD, between > 30% and 70% of expected. After some spec reading it seems like even if > there is no fail over penalty for switching between SVC cluster node > members there is of course a penalty since each SVC has 8GB of cache. > So keeping your IO to one controller is a good idea. > > However the only way I think I can identify which SVC is the target > node_name information (/sys/class/fc_transport/target0\:0\:0/node_name > ), so I have to look that up somehow, I am currently unable to figure > out how from a block device find the target using /sys. > Doesn't the box give usable serials on SCSI INQ ? The multipath tool already fetches that (you can see the values when debug is enabled), and proposes to group by these strings. I guess it could be useful to fetch the target node_name anyway. > I assume that once I done this all I need to do is write my own > priority finding program that looks these up and groups them into a > priority depending on the target node_name / > Might work too. > Thanks for the work on this, we were able to add a second lun, add it > to our lvm group and then grow the filesystem on top of it without any > downtime! > So you owe me an entry in the TestedEnvironments page in the Wiki :) regards, -- christophe varoqui <christophe.varoqui@xxxxxxx>