Using lvmstat

One of the best tools to look at LVM usage is with lvmstat. It can report the bytes read and written to logical volumes. Using that information, you can determine which logical volumes are used the most.

Gathering LVM statistics is not enabled by default:

# lvmstat -v data2vg
0516-1309 lvmstat: Statistics collection is not enabled for
        this logical device. Use -e option to enable.

As you can see by the output here, it is not enabled, so you need to actually enable it for each volume group prior to running the tool using:

# lvmstat -v data2vg -e

The following command takes a snapshot of LVM information every second for 10 intervals:

# lvmstat -v data2vg 1 10

This view shows the most utilized logical volumes on your system since you started the data collection. This is very helpful when drilling down to the logical volume layer when tuning your systems.

# lvmstat -v data2vg

Logical Volume    iocnt   Kb_read  Kb_wrtn   Kbps
  appdatalv      306653  47493022   383822  103.2
  loglv00            34         0     3340    2.8
  data2lv           453    234543   234343   89.3         

What are you looking at here?

• iocnt: Reports back the number of read and write requests.
• Kb_read: Reports back the total data (kilobytes) from your measured interval that is read.
• Kb_wrtn: Reports back the amount of data (kilobytes) from your measured interval that is written.
• Kbps: Reports back the amount of data transferred in kilobytes per second.

You can use the -d option for lvmstat to disable the collection of LVM statistics.