Hi I have got a couple of MD3000i with dual controllers, and two M600e blades connected two both of them. I've setup multipath, and would appreciate if someone could tell me whether the setup described below looks correct, or if you'd do it any other way. The reason I'm asking, is that I cannot see any reference to 'rdac hardware handler' when I do "multipath -ll". However, when I change the module controller ownership one of the LUNs (while copying files to that particular LUN), the failover seems to work - the gilr copying continues after the controller switch. I also see these messages in /var/log/messages when I change the module controller ownership: 494 [RAIDarray.mpp]MD3000i_A:0:1:0 Cmnd-failed try alt ctrl 1. vcmnd SN 351494 pdev H2:C0:T0:L0 0x05/0x94/0x01 0x08000002 mpp_status:1 Q1: What could be the reason that I'm not using the rdac hwhandler ? (see output from "multipath -ll" below) Q2: Is using rdac for this kind of setup preferred ? Q3: I've created a GPFS filesystem using the /dev/dm-0, /dev/dm-1, etc device. Is it OK to use the dm-x devices ? I see that there are other alternatives such as /dev/mapper/mpath<x>. However, /dev/mapper/mpath<x> is not visible in /proc/partitions (see below), but the dm-<x> devices are - and the GPFS filesystem complains when it cannot see the devices in /proc/partitions. Q4: Does my setup described here look OK ? The blades are running: SLES 10 SP2 (x86-64) From the MD3000i Dell Resource CD the following rpm was installed: linuxrdac-09.03.0C06.0030-1dkms The following modules are running on my blades: # lsmod | egrep 'rdac|mpp|multi' dm_rdac 24832 0 dm_multipath 42640 3 dm_rdac,dm_round_robin dm_mod 80528 26 dm_multipath mppVhba 145120 24 mppUpper 127436 1 mppVhba scsi_mod 170936 12 dm_rdac,iscsi_tcp, libiscsi, scsi_transport_iscsi, mptctl,mppVhba,mptsas, mptscsih, scsi_transport_sas, mppUpper,sg,sd_mod My multipath.conf file contains: #cat /etc/multipath.conf defaults { udev_dir /dev user_friendly_names yes } blacklist { devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*" devnode "^hd[a-z]" devnode "^sda" devnode "^sda[0-9]" device { vendor DELL product "PERC|Universal" } } devices { device { vendor "DELL" product "MD3000i" product_blacklist "Universal Xport" features "1 queue_if_no_path" path_grouping_policy group_by_prio hardware_handler "1 rdac" path_checker rdac prio "rdac" failback immediate } } multipaths { mulitpath { device { vendor DELL product MD3000i } } } After changing the multipath.conf I did: multipath -F service multipathd restart Now, if I've do: # multipath -ll mpathe (36002219000918b4c00005b6c497e6632) dm-4 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:1 sdi 8:128 [active][ready] mpathd (36002219000918b3300002e6e497e6315) dm-3 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:2 sdj 8:144 [active][ready] mpathc (36002219000918b4c00005b6f497e6695) dm-2 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:3 sdk 8:160 [active][ready] mpathb (36002219000918b3300002e71497e6378) dm-1 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:4 sdl 8:176 [active][ready] mpatha (36002219000918b4c00005b72497e66f3) dm-0 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:5 sdm 8:192 [active][ready] mpathl (36002219000918b3300002e6b497e62a6) dm-11 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:0:0 sdb 8:16 [active][ready] mpathk (36002219000922cdf000004a4497e53f5) dm-10 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:10 sdc 8:32 [active][ready] mpathj (36002219000918b2e000004b2497e581c) dm-9 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:11 sdd 8:48 [active][ready] mpathi (36002219000922cdf000004a7497e54dd) dm-8 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:12 sde 8:64 [active][ready] mpathh (36002219000918b2e000004b5497e587e) dm-7 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:13 sdf 8:80 [active][ready] mpathg (36002219000922cdf000004aa497e5532) dm-6 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:14 sdg 8:96 [active][ready] mpathf (36002219000918b2e000004b8497e58dc) dm-5 DELL,MD Virtual Disk [size=5.5T][features=0][hwhandler=0] \_ round-robin 0 [prio=1][active] \_ 9:0:1:15 sdh 8:112 [active][ready] cat /proc/partitions major minor #blocks name 8 0 71041024 sda 8 1 530113 sda1 8 2 8393962 sda2 8 3 62115322 sda3 8 16 5857419264 sdb 8 32 5857419264 sdc 8 48 5857419264 sdd 8 64 5857419264 sde 8 80 5857419264 sdf 8 96 5857419264 sdg 8 112 5857419264 sdh 8 128 5857419264 sdi 8 144 5857419264 sdj 8 160 5857419264 sdk 8 176 5857419264 sdl 8 192 5857419264 sdm 253 0 5857419264 dm-0 253 1 5857419264 dm-1 253 2 5857419264 dm-2 253 3 5857419264 dm-3 253 4 5857419264 dm-4 253 5 5857419264 dm-5 253 6 5857419264 dm-6 253 7 5857419264 dm-7 253 8 5857419264 dm-8 253 9 5857419264 dm-9 253 10 5857419264 dm-10 253 11 5857419264 dm-11 Thank you Christian