Veritas File System 5.0 Administrator's Guide (September 2006)

<DELETE>
<FROM>
<SOURCE>
<CLASS>tier3</CLASS>
</SOURCE>
</FROM>
</DELETE>
<DELETE>
<FROM>
<SOURCE>
<CLASS>tier2</CLASS>
</SOURCE>
</FROM>
<WHEN>
<ACCAGE Units="days">
<MIN Flags="gt">120</MIN>
</ACCAGE>
</WHEN>
</DELETE>
The first DELETE statement unconditionally deletes files designated by the rule's
SELECT statement that reside on tier3 volumes when the fsppadm enforce
command is issued. The absence of a <WHEN> clause in the DELETE statement
indicates that deletion of designated files is unconditional.
The second DELETE statement deletes files to which the rule applies that reside
on tier2 volumes when the fsppadm enforce command is issued and that have
not been accessed for the past 120 days.
Calculating I/O temperature and access temperature
An important application of VxFS Dynamic Storage Tiering is automating the
relocation of inactive files to lower cost storage. If a file has not been accessed for
the period of time specified in the <ACCAGE> element, a scan of the file system
should schedule the file for relocation to a lower tier of storage. But, time since
last access is inadequate as the only criterion for activity-based relocation.
Why time since last access is inadequate as the only criterion for activity-based
relocation:
■ Access age is a binary measure. The time since last access of a file is computed
by subtracting the time at which the fsppadm enforce command is issued
from the POSIX atime in the file's metadata. If a file is opened the day before
the fsppadm enforce command, its time since last access is one day, even
Dynamic Storage Tiering
Calculating I/O temperature and access temperature
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