Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

<WHEN>

</IOTEMP>

</WHEN>

</RELOCATE>

If there are a number of files whose I/O temperature is greater than the given

minimum value, the files with the higher temperature are first subject to the

RELOCATE operation before the files with the lower temperature.

Average I/O activity

The Average criteria allows you to specify the value of the I/O temperature as a

ratio of per-file activity that occurs over the time specified by the <PERIOD> element

compared to the overall file system activity that occurs over a longer period of

time. The <PERIOD> element in the RELOCATE criteria specifies the a number of

hours or days immediately before the time of the scan. During that time, the I/O

statistics that are collected are used to process the files that are being scanned.

Since I/O activity can change over time, collect the average I/O activity over a

longer duration than the <PERIOD> value itself, which is by default 24 hours. Doing

so lets you compute an average temperature of the whole file system. Symantec

recommends that you specify an Average attribute value only if you are using

solid state disks (SSDs).

See “Average I/O activity” on page 380.

The following placement policy snippet gives an example of the Average criteria:

...

<WHEN>

</IOTEMP>

</WHEN>

</RELOCATE>

In the snippet, VxFS relocates any file whose read IOTEMP over the last 6 hours

is 1.5 times that of all the active files in the whole file system over the last 24

hours. This Average criteria is more intuitive and easier to specify than the

absolute values.

361Administering SmartTier

File placement policy rules