Veritas File System 5.0 Administrator's Guide (September 2006)
Including a <MIN> element in a <WHEN> clause causes VxFS to relocate files to
which the rule applies that have been inactive for longer than the specified interval.
Such a rule would typically be used to relocate inactive files to less expensive
storage tiers. Conversely, including <MAX> causes files accessed within the specified
interval to be relocated. It would typically be used to move inactive files against
which activity had recommenced to higher performance or more reliable storage.
Including both <MIN> and <MAX> causes VxFS to relocate files whose access age
lies between the two.
The modification age relocation criterion, <MODAGE>, is similar to access age, except
that files' POSIX mtime values are used in computations. You would typically
specify the <MODAGE> criterion to cause relocation of recently modified files to
higher performance or more reliable storage tiers in anticipation that the files
would be accessed recurrently in the near future.
The file size relocation criterion, <SIZE>, causes files to be relocated if the files
are larger or smaller than the values specified in the <MIN> and <MAX> relocation
criteria, respectively, at the time that the fsppadm enforce command was issued.
Specifying both criteria causes VxFS to schedule relocation for files whose sizes
lie between the two. Using the Units attribute, threshold file sizes may be specified
in the following units:
Bytesbytes
KilobytesKB
MegabytesMB
GigabytesGB
Specifying the I/O temperature relocation criterion
The I/O temperature relocation criterion, <IOTEMP>, causes files to be relocated
if their I/O temperatures rise above or drop below specified values over a specified
period immediately prior to the time at which the fsppadm enforce command
was issued. A file's I/O temperature is a measure of the read, write, or total I/O
activity against it normalized to the file's size. Higher I/O temperatures indicate
higher levels of application activity; lower temperatures indicate lower levels.
VxFS computes a file's I/O temperature by dividing the number of bytes transferred
to or from it (read, written, or both) during the specified period by its size at the
time that the fsppadm enforce command was issued.
As with the other file relocation criteria, <IOTEMP> may be specified with a lower
threshold by using the <MIN> element, an upper threshold by using the <MAX>
165Dynamic Storage Tiering
File placement policy rules