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

■ Support of the Prefer attribute for the <IOTEMP> and <ACCESSTEMP> criteria

■ Provision of a mechanism to relocate based on average I/O activity

■ Reduction of the intensity and duration of scans to minimize the impact on

resources, such as memory, CPU, and I/O bandwidth

■ Quick identification of cold files

To gain these benefits, you must modify the existing placement policy as per the

latest version of the DTD and assign the policy again. However, existing placement

policies continue to function as before. You do not need to update the placement

policies if you do not use the new features.

Fine grain temperatures

Before the solid state disk (SSD) enhancements, the SmartTier feature computed

temperature values on a day granularity. Day granularity is the I/O activity per

day over at least one day. As such, the <PERIOD> element had to be in days for the

<IOTEMP> and <ACCESSTEMP> criteria. With SSDs, relocation decisions might need

to happen within the day itself, based on I/O activity that Veritas File System

(VxFS) measured over a shorter duration. As such, you can now specify "hours"

for the Units attribute value for the <IOTEMP> and <ACCESSTEMP> criteria.

See “Specifying the I/O temperature relocation criterion” on page 359.

The following placement policy snippet gives an example of specifying 4 hours

as the period of time:

...

<WHEN>

</IOTEMP>

</WHEN>

</RELOCATE>

Prefer mechanism

You can now specify a value for the Prefer attribute for the <IOTEMP> and

<ACCESSTEMP> criteria, which gives preference to relocating files.

See “Prefer attribute” on page 360.

In case of a solid state disk (SSD)-based tier, you might want to relocate a file to

an SSD as soon as there is a marked increase in the I/O activity. However, once

379Administering SmartTier

Using SmartTier with solid state disks