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dmz1213 01-28-2013 06:27 PM

DM device on virtual machine
 
On a virtual redhat, command
# fdisk -l
Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 33 265041 83 Linux
/dev/sda2 34 2610 20699752+ 8e Linux LVM
#
# iostat 1 10

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 96.00 4624.00 0.00 4624 0
sda1 0.00 0.00 0.00 0 0
sda2 96.00 4624.00 0.00 4624 0
dm-0 6.00 248.00 0.00 248 0
dm-1 0.00 0.00 0.00 0 0

dm-6 0.00 0.00 0.00 0 0
dm-7 543.00 4344.00 0.00 4344 0
dm-8 1.00 8.00 0.00 8 0
How can I identify what those dm devices are? Especially dm-7. It has quite bit I/O activity. This is a virtual machine (ESX).
# service multipathd status
multipathd is stopped
Red Hat Enterprise Linux Server release 5.5 (Tikanga).
Thanks.

Kustom42 01-28-2013 06:34 PM

Here is some info:


https://access.redhat.com/knowledge/...onfigfile.html
https://access.redhat.com/knowledge/...ce_mapper.html


Basically the device mapper config file should have the device mappings to the dm-* names.

You can also try using the dmsetup info device name command.

dmz1213 01-28-2013 07:19 PM

Thanks to Kustom42.
Command dmsetup info and dmsetup ls provide good information.
To confirm that, I compare Major/minor number that dmsetup info shows to /sys/block/dm-7/dev. dm-7 is swaplv


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