This chapter discusses the following:
 | Note: The examples in this chapter assume that statistics have been
turned on for the objects shown.
Accurate statistics are not displayed for volumes; the output shows "0" for all fields. |
XVM can maintain statistics for physvols, subvolumes, stripes, concats, mirrors, and slices.
You use the stat option of the change command to enable/disable the collection of statistics and to reset the statistics for a volume element. Statistics are on by default. Statistics are enabled/disabled only for the specified layer of the XVM volume topology tree. If you want to collect statistics for multiple layers, you must specify each layer explicitly.
In a clustered environment, statistics are maintained for the local node only.
Statistics for all volume elements and physical volume (physvols) show the number of read and write operations as well as the number of 512-byte blocks read and written.
You can display statistics by using either show -stat or show -v in the xvm CLI.
The following example displays the statistics of a physvol for which statistics have been turned on:
xvm:cluster> show -stat betty Local stats for phys/betty since being enabled or reset: ---------------------------------------------------------------------- client read requests: 3 client write requests: 42 client 512 byte blks read: 257 client 512 byte blks written: 4681 |
Subvolume statistics show the number of read/write requests and the number of 512-byte blocks read/written. For example:
xvm:cluster> show -stat subvol/Stat/data Local stats for subvol/Stat/data since being enabled or reset: --------------------------------------------------------------------- read requests: 165 write requests: 32 512 byte blks read: 1958 512 byte blks written: 4096 |
Stripe statistics show the size of the operations versus the size of the stripe width and whether the operations are aligned on a 512-byte boundary. The best performance is obtained when the greatest number of requests are aligned at both start and end. For example:
xvm:cluster> show -stat stripe/stripe356
Local stats for stripe/stripe356 since being enabled or reset:
--------------------------------------------------------------------
read requests: 165
write requests: 32
512 byte blks read: 1958
512 byte blks written: 4096
Requests aligned at both start and end
equal to stripe width: 46
greater than stripe width: 0
less than stripe width: 0
Requests aligned at start
greater than stripe width: 0
less than stripe width: 6
Requests aligned at end
greater than stripe width: 0
less than stripe width: 4
Requests unaligned
equal to stripe width: 0
greater than stripe width: 0
less than stripe width: 141
|
Concat statistics show the number of operations that are straddled, which are operations that cross the boundary between one piece and the next. For example:
xvm:cluster> show -stat concat/concat178 Local stats for concat/concat178 since being enabled or reset: ------------------------------------------------------------------- read requests: 165 write requests: 32 512 byte blks read: 1958 512 byte blks written: 4096 reads straddling slices: 0 writes straddling slices: 0 |
Mirror statistics show the read/write requests and the mirror synchronization reads/writes. For example:
xvm:cluster> show -stat mirror/mirror265 Local stats for mirror/mirror265 since being enabled or reset: ------------------------------------------------------------------- read requests: 165 write requests: 32 512 byte blks read: 1958 512 byte blks written: 4096 Mirror synchronization reads: 0 Mirror synchronization writes: 0 Leg Reads Writes 0 165 32 |
Slice statistics show the number of read/write operations and the number of 512-byte blocks read/written. For example:
xvm:cluster> show -stat slice/temps0 Local stats for slice/temps0 since being enabled or reset: -------------------------------------------------------------------- read requests: 165 write requests: 32 512 byte blks read: 1958 512 byte blks written: 4096 |