I have inherited a system set up with multipath, which is not something I have seen before so I could use some advice The system is a Dell R420 with 2 LSI SAS2008 HBAs, 4 internal disks, and a MD3200 storage array attached via SAS cables. Oh and CentOS 6 lsblk shows the following: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sdd 8:48 0 931.5G 0 disk ├─sdd1 8:49 0 931.5G 0 part └─mpathi (dm-0) 253:0 0 931.5G 0 mpath sdc 8:32 0 931.5G 0 disk ├─sdc1 8:33 0 1000M 0 part /boot ├─sdc2 8:34 0 31.3G 0 part / ├─sdc3 8:35 0 31.3G 0 part [SWAP] ├─sdc4 8:36 0 1K 0 part ├─sdc5 8:37 0 184.5G 0 part /home └─sdc6 8:38 0 683.6G 0 part /data01 sde 8:64 0 931.5G 0 disk ├─sde1 8:65 0 931.5G 0 part └─mpathj (dm-1) 253:1 0 931.5G 0 mpath └─mpathjp1 (dm-8) 253:8 0 931.5G 0 part /data02 sdf 8:80 0 931.5G 0 disk ├─sdf1 8:81 0 931.5G 0 part └─mpathk (dm-2) 253:2 0 931.5G 0 mpath sda 8:0 0 51T 0 disk ├─sda1 8:1 0 12.8T 0 part ├─sda2 8:2 0 12.8T 0 part ├─sda3 8:3 0 12.8T 0 part ├─sda4 8:4 0 12.8T 0 part └─mpathe (dm-3) 253:3 0 51T 0 mpath ├─mpathep1 (dm-4) 253:4 0 12.8T 0 part /SAN101 ├─mpathep2 (dm-5) 253:5 0 12.8T 0 part /SAN102 ├─mpathep3 (dm-6) 253:6 0 12.8T 0 part /SAN103 └─mpathep4 (dm-7) 253:7 0 12.8T 0 part /SAN104 sdb 8:16 0 51T 0 disk ├─sdb1 8:17 0 12.8T 0 part ├─sdb2 8:18 0 12.8T 0 part ├─sdb3 8:19 0 12.8T 0 part ├─sdb4 8:20 0 12.8T 0 part └─mpathe (dm-3) 253:3 0 51T 0 mpath ├─mpathep1 (dm-4) 253:4 0 12.8T 0 part /SAN101 ├─mpathep2 (dm-5) 253:5 0 12.8T 0 part /SAN102 ├─mpathep3 (dm-6) 253:6 0 12.8T 0 part /SAN103 └─mpathep4 (dm-7) 253:7 0 12.8T 0 part /SAN104 sda and sdb are two views of the unit on the MD, sdc is the boot and root disk, one of the disks sde (mpathj) has a mounted file system, the remaining two do not. here is df: Filesystem Type Size Used Avail Use% Mounted on /dev/sdc2 ext4 31G 26G 4.0G 87% / tmpfs tmpfs 16G 92K 16G 1% /dev/shm /dev/sdc1 ext4 969M 127M 793M 14% /boot /dev/sdc6 ext4 673G 242G 398G 38% /data01 /dev/mapper/mpathjp1 ext4 917G 196G 676G 23% /data02 /dev/sdc5 ext4 182G 169G 3.9G 98% /home /dev/mapper/mpathep1 ext4 13T 11T 1005G 92% /SAN101 /dev/mapper/mpathep2 ext4 13T 5.0T 7.0T 42% /SAN102 /dev/mapper/mpathep3 ext4 13T 4.9T 7.1T 42% /SAN103 /dev/mapper/mpathep4 ext4 13T 8.2T 3.8T 69% /SAN104 So a few questions: Is there any value in using multipath on the 4 internal drives; do they actually have multiple data paths? Why does multipath not create a mpath device for the system disk sdc, there is no blacklist in the mulitpath.conf file. If I do a dry-run mulitpath -d command, it sets up mpathh on sdc, but apparently not on boot. Why not? I should say that the system has not been rebooted since well before I took it over, it has been up for over 400 days. the sdd and sdf disks have a single partition, but apparently no mpath device for the partition, how to I create one? Thanks in advance