Hello List, I'm currently facing a problem with a storage virtualization device which is located in two different datacenters and shows up as another path to a configured SAN-LUN. The virtualization device is from EMC² and is called V-PLEX. So I have something like this: DC A Host ---VPLEX-DC A---LUN storage A | | ..|...........|................... | DC B | ------VPLEX-DC B---LUN storage B The VPLEX device itself is for storage based mirroring and synchronizes write access to storage A to storage B and the other way around. My problem is, that the virtual LUN I get from the VPLEX does not have any prioritization given by dm-multipath and looks like this: mpath3 (36000144000000010e06d8f12ec30dfef) dm-9 EMC,Invista [size=5.0G][features=1 queue_if_no_path][hwhandler=0][rw] \_ round-robin 0 [prio=1][active] \_ 5:0:1:2 sdad 65:208 [active][ready] \_ 5:0:4:2 sdak 66:64 [active][ready] \_ 5:0:5:2 sdap 66:144 [active][ready] \_ 4:0:0:2 sdc 8:32 [active][ready] \_ 4:0:1:2 sdh 8:112 [active][ready] \_ 4:0:4:2 sdo 8:224 [active][ready] \_ 4:0:5:2 sdt 65:48 [active][ready] \_ 5:0:0:2 sdy 65:128 [active][ready] That way, write access is made round-robin and access to the "remote-devices" - device located in the other DC - creating duplicate traffic through the SAN switches as the access has to be routed to the remote VPLEX-B and it will write to the local VPLEX-A. I wanted to solve this problem by giving priorities to a path by its remote-port - which is different for each connection to a SAN device. Unfortunately there currently doesn't exist any priorizer and I have to write one on my own. To make the definition flexible, I would like to have a file with a list of port-wwns associated with a priority. For versions shipped with RHEL5 this could be a simple shell script which simply looks up the sysfs file structures of a given device. For RHEL6 this has to be a binary library. So writing a binary version will make more sense than maintaining two different solutions. A P-o-c script I wrote runs fine on RHEL5 - althouh a bit slow - but shows the results I wanted to see: --------- script -------- #! /bin/bash PRIO_DEF="/etc/dm-multipath-vplex.conf" DEVICE=${1#/dev/*} # find scsi-device address SCSI_ADDR="$(basename $(readlink /sys/block/$DEVICE/device/scsi_device*) )" # 3:0:2:0 # remove trailing :0 SCSI_ADDR=${SCSI_ADDR%:*} # 3:0:2 # change x:x:x to x:x-x SCSI_ADDR=$(echo "$SCSI_ADDR" | sed -e 's/:$[0-9]$$/-\1/' ) # get port_name for scsi-remote-port RPORT=$(cat "/sys/class/fc_remote_ports/rport-$SCSI_ADDR/port_name") # return prio IGNORECASE=1 awk "/$RPORT/ { print \$1 }" $PRIO_DEF ------------------------------------------ ---------- dm-multipath-vplex.conf -------- # VPLEX DC A 1 0x50001442606d8f00 1 0x50001442606d8f01 1 0x50001442606d8f02 1 0x50001442606d8f03 1 0x50001442706d8f00 1 0x50001442706d8f01 1 0x50001442706d8f02 1 0x50001442706d8f03 # VPLEX DC B 2 0x5000144260641900 2 0x5000144260641901 2 0x5000144260641902 2 0x5000144260641903 2 0x5000144270641900 2 0x5000144270641901 2 0x5000144270641902 2 0x5000144270641903 -------------------------------------------- Do you think that this solutions is worth including it as rport-prio into device mappers source? My C language skills are a bit rusty, but I at least managed to find out the SCSI-address of a given device and build the sysfs-path to the remote port. The rest should also be manageable, but I wanted to ask as early a possible to have it included into mainstream and get some feedback on this. Best regrads, Andreas Bleischwitz