How can I map iostat device names to LVM /dev/mapper/XXX names?

Question

mount shows mount devices like:

/dev/mapper/VolGroup01-LogVol00 on /var type ext3 (rw)

or

/dev/mapper/VolGrp_backups-backups on /mnt/backups type ext3 (rw)

but

iostat uses dm- notation. like dm-0, dm-1 and so on.

Where can I find a way to know which is which?

Somehow, I thought there was a way to tell iostat to 'just do that', but there isn't one (that I can find). +1 for a great question that got an answer that helped me too. — Tim Post, May 17 '11 at 17:16

score 22 · Accepted Answer · edited May 17 '11 at 17:14

22

ls -l /dev/mapper/*, the device minor number (field 6 of what ls -l outputs) corresponds to the number in dm-\d+.

edited May 17 '11 at 17:14

Tim Post

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answered Nov 24 '09 at 14:30

womble

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Mark Wagner · Answer 2 · 2011-05-17T18:46:40.737

13

Depending on the version of iostat you have the -N option will do this for you:

-N Display the registered device mapper names for any device mapper devices. Useful for viewing LVM2 statistics.

Edit: versions >= 7.1.4 of systat (which includes iostat) have that option.

2007/04/29: Version 7.1.4 - Sebastien Godard (sysstat wanadoo.fr) * Option -N added to iostat. This option enables the user to query any device-mapper devices for their registered device name [bugzilla #177540].

edited May 17 '11 at 18:46

answered May 17 '11 at 18:41

Mark Wagner

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a more accurate answer for the question. – Felipe Alvarez Nov 26 '15 at 06:04

score 4 · Answer 3 · edited Apr 04 '15 at 18:24

you can try lsblk command which shows the Logical Volume used by respective dev-mapper.

# lsblk
NAME                       MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                          8:0    0    8G  0 disk
├─sda1                       8:1    0  500M  0 part /boot
└─sda2                       8:2    0  7.5G  0 part
  ├─vg_root-lv_root (dm-0) 253:0    0  5.6G  0 lvm  /
  └─vg_root-lv_swap (dm-1) 253:1    0    2G  0 lvm  [SWAP]
sdb                          8:16   0  200M  0 disk
sdc                          8:32   0  1.5G  0 disk
sdd                          8:48   0  512M  0 disk
sde                          8:64   0    4G  0 disk
└─vg_root-lv_data (dm-2)   253:2    0  3.5G  0 lvm  /data1

score 1 · Answer 4 · edited Dec 16 '13 at 19:07

1

Please try this command in version of iostat where there is no -N option to list the LV's

lvdisplay | awk '/LV Name/{blockdev=$3} /Block device/{bdid=$3; sub("[0-9]*:","dm-",bdid); print bdid,blockdev;}'

edited Dec 16 '13 at 19:07

Aaron Copley

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answered Dec 16 '13 at 16:31

user202677

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score 1 · Answer 5 · answered Mar 14 '19 at 20:43

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The correct and easiest way to do it is to use the following command:

iostat -Nd

From the man page of iostat, the option -N already displays the registered device mapper names.

answered Mar 14 '19 at 20:43

user3801989

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What does this answer add over Mark Wagner's answer from 2011? – womble Mar 15 '19 at 07:29

score 0 · Answer 6 · edited Jul 14 '16 at 17:02

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You can use a simple lvdisplay with awk, like this.

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

edited Jul 14 '16 at 17:02

chicks

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answered Jul 14 '16 at 16:13

Diego Roberto Dos Santos

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score 0 · Answer 7 · answered Oct 14 '19 at 07:49

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Cleanest, simplest output: ls -lrt /dev/mapper

answered Oct 14 '19 at 07:49

Gaia

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How can I map iostat device names to LVM /dev/mapper/XXX names?

7 Answers7