LVM / device-mapper statistics
==============================

lvmstats is a simple userspace tool to configure, control, and report
device-mapper IO statistics.

Usage
=====

  Usage: lvmstat [command] [options] [ device [...] | ALL ] [ interval [ count ] ]

  Commands:

         lvstat [options] [LogicalVolumeName [VolumeGroupName...]]

  -h, --help            show this help message and exit
  -c, --cpu             Display the CPU utilization report.
  -x, --extended        Display extended statistics.
  -s, --segments        Display statistics by segments.
  -e, --extents         Display statistics by extents.
  -a SIZE, --areas=SIZE
                        Display statistics by areas of size SIZE.
  -n NR_AREAS, --nr-areas=NR_AREAS
                        Display statistics by NR_AREAS areas.
  -k, --kilobytes       Display statistics in kilobytes per second.
  -m, --megabytes       Display statistics in megabytes per second.
  -t, --times           Print the time for each report
  -D                    Display debugging information


Output
======

Device Utilization Report

The output of lvmstat mimics the output of the iostat program allowing
the reuse of existing iostat parsing and graphing tools.

The extended output format is as follows:

The device report provides statistics for each configured device region.
The device-mapper devices for which statistics are to be displayed may
be entered on the command line.  If no device nor partition is entered,
then statistics are displayed for every device-mapper device used by the
system.  Transfer rates are  shown in 1K  blocks by default, unless the
environment variable POSIXLY_CORRECT is set, in which case 512-byte
blocks are used.  The report may show the following fields, depending on
the flags used:

    Device:
           This column gives the device (or partition) name as
           listed in the /dev directory.

    tps
           Indicate the number of transfers per second that
           were issued to the device. A transfer is an I/O request to
           the device. Multiple logical requests  can be combined into
           a single I/O request to the device. A transfer is of
           indeterminate size.

    Blk_read/s (kB_read/s, MB_read/s)
           Indicate  the  amount of data read from the device
           expressed in a number of blocks (kilobytes, megabytes) per
           second. Blocks are equivalent to sectors and therefore have
           a size of 512 bytes.

    Blk_wrtn/s (kB_wrtn/s, MB_wrtn/s)
           Indicate the amount of data written to the device
           expressed in a number of blocks (kilobytes, megabytes) per
           second.

    Blk_read (kB_read, MB_read)
           The total number of blocks (kilobytes, megabytes)
           read.

    Blk_wrtn (kB_wrtn, MB_wrtn)
           The total number of blocks (kilobytes, megabytes)
           written.

    rrqm/s
           The number of read requests merged per second that
           were queued to the device.

    wrqm/s
           The number of write requests merged per second that
           were queued to the device.

    r/s
           The number (after merges) of read requests
           completed per second for the device.

    w/s
           The number (after merges) of write requests
           completed per second for the device.

    rsec/s (rkB/s, rMB/s)
           The number of sectors (kilobytes, megabytes) read
           from the device per second.

    wsec/s (wkB/s, wMB/s)
           The number of sectors (kilobytes, megabytes)
           written to the device per second.

    avgrq-sz
           The average size (in sectors) of the requests that
           were issued to the device.

    avgqu-sz
           The average queue length of the requests that were
           issued to the device.

    await
           The average time (in milliseconds) for I/O requests
           issued to the device to be served. This includes the time
           spent by the requests in queue  and  the time spent
           servicing them.

    r_await
           The  average time (in milliseconds) for read
           requests issued to the device to be served. This includes
           the time spent by the requests in queue and the time spent
           servicing them.

    w_await
           The average time (in milliseconds) for write
           requests issued to the device to be served. This includes
           the time spent by the requests in queue and the time spent
           servicing them.

    svctm
           The  average  service  time  (in milliseconds) for
           I/O requests that were issued to the device. FIXME: verify
           accuracy of this derived metric for dm devices.

    %util
	   Percentage of CPU time during which I/O requests were issued
           to the device (bandwidth utilization for the device). Device
           saturation occurs when this value is close to 100%.