How do I know what physical drives/partitions are behind my /dev/mapper/isw_dghbbcaabe_RAID_Volume11?

Question

This is a just upgraded Ubuntu 10.04.1 LTS machine.

The /dev/mapper/isw_dghbbcaabe_RAID_Volume11 is "new" to the upgrade but I don't know what physical drives/partitions are included in the "device".

I have tried:

root@barabasi:~# blkid   
/dev/sda1: UUID="8258e116-265a-4797-59d1-fae72a643620" TYPE="swap" 
/dev/sdb: TYPE="isw_raid_member" 
/dev/mapper/isw_dghbbcaabe_RAID_Volume11: UUID="1d4721b1-5649-4772-8a03-5c3db81eba1b" TYPE="ext3" 
/dev/mapper/isw_dghbbcaabe_RAID_Volume15: UUID="b9a639af-dee8-4e0c-90f6-15432efac4f2" TYPE="swap"

and

root@barabasi:~# ls -alh /dev/disk/by-uuid/  
total 0 
drwxr-xr-x 2 root root 100 2011-01-14 12:49 . 
drwxr-xr-x 5 root root 100 2011-01-14 12:49 .. 
lrwxrwxrwx 1 root root 41 2011-01-14 12:49 1d4721b1-5649-4772-8a03-5c3db81eba1b ->    ../../mapper/isw_dghbbcaabe_RAID_Volume11 
lrwxrwxrwx 1 root root 10 2011-01-14 12:49 8258e116-265a-4797-59d1-fae72a643620 -> ../../sda1 
lrwxrwxrwx 1 root root 41 2011-01-14 12:49 b9a639af-dee8-4e0c-90f6-15432efac4f2 -> ../../mapper/isw_dghbbcaabe_RAID_Volume15

But I still don't know what physical drives are involved.

Answer 1

Best quick overview I have seen is lsblk, which prints a reasonable output even if you have a complicated setup.

$ lsblk
NAME                     MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                        8:0    0 223,6G  0 disk 
├─sda1                     8:1    0   350M  0 part 
├─sda2                     8:2    0    29G  0 part 
├─sda3                     8:3    0   488M  0 part /boot
├─sda4                     8:4    0     1K  0 part 
└─sda5                     8:5    0 193,8G  0 part 
  ├─vg_ssd-lv_root_solid 254:0    0  13,3G  0 lvm  /
  ├─vg_ssd-lv_srv_solid  254:2    0  46,6G  0 lvm  /srv
  └─vg_ssd-lv_home_solid 254:3    0   107G  0 lvm  /home
sdb                        8:16   0  74,5G  0 disk 
└─sdb1                     8:17   0  74,5G  0 part 
  ├─vg_ssd-lv_swap_solid 254:1    0   3,7G  0 lvm  [SWAP]
  └─vg_ssd-lv_videos     254:4    0    28G  0 lvm  /mnt/videos

See also: this more detailed answer on server fault.

Answer 2

I found the easiest command is -

$ sudo dmsetup deps -o devname

Which gives you the actual device name without the need to figure out the major/minor numbers.

Answer 3

Or just execute the following command:

$ sudo dmsetup ls --tree

which will show how your block devices are stacked.

Answer 4

You can use dmsetup. Invoke:

$ sudo dmsetup -v table /dev/mapper/isw_dghbbcaabe_RAID_Volume11

That will give you a list of sectors which are mapped to another device. In my case (encrypted root partition), I get the following output:

$ sudo dmsetup table /dev/mapper/hacki-mobile 
0 567028121 crypt aes-cbc-essiv:sha256 0000000000000000000000000000000000000000000000000000000000000000 0 8:6 2056

That means that sectors 0-567028121 are mapped to a device with major/minor number 8/6. That is the 6th partition on my sda drive, as you can see with:

$ ls -Al /dev/sda6
brw-rw---- 1 root disk 8, 6 2010-12-21 14:38 /dev/sda6

Your output from dmsetup maybe a bit different, as I'm on Ubuntu 10.04

Answer 5

Below are some examples.

lvs -o +devices
lvdisplay -m
lvdisplay | awk '/LV Name/{n=$3} /Block device/{d=$3; sub(".*:","dm-",d); print d,n;}'

Answer 6

This is just a hint! Because I came to this question and found an answer by myself.

Sometimes you can use ls -lha /dev/mapper/ or similar to see the mapped devices and you can use mount to resolve it.