Veritas™ File System 5.0.1 Administrator's Guide

The following example illustrates of three placement classes specified in the <ON>
clause of a CREATE statement:
<CREATE>
<ON>
<DESTINATION>
<CLASS>tier1</CLASS>
</DESTINATION>
<DESTINATION>
<CLASS>tier2</CLASS>
</DESTINATION>
<DESTINATION>
<CLASS>tier3</CLASS>
</DESTINATION>
</ON>
</CREATE>
In this statement, VxFS would allocate space for newly created files designated
by the rule's SELECT statement on tier1 volumes if space was available. If no
tier1 volume had sufficient free space, VxFS would attempt to allocate space on
a tier2 volume. If no tier2 volume had sufficient free space, VxFS would attempt
allocation on a tier3 volume. If sufficient space could not be allocated on a volume
in any of the three specified placement classes, allocation would fail with an
ENOSPC error, even if the file system's volume set included volumes in other
placement classes that did have sufficient space.
The <TO> clause in the RELOCATE statement behaves similarly. VxFS relocates
qualifying files to volumes in the first placement class specified if possible, to
volumes in the second specified class if not, and so forth. If none of the destination
criteria can be met, such as if all specified classes are fully occupied, qualifying
files are not relocated, but no error is signaled in this case.
Multiple placement classes in <FROM> clauses of RELOCATE and
DELETE statements
The <FROM> clause in RELOCATE and DELETE statements can include multiple source
placement classes. However, unlike the <ON> and <TO> clauses, no order or priority
is implied in <FROM> clauses. If a qualifying file resides on a volume in any of the
placement classes specified in a <FROM> clause, it is relocated or deleted regardless
of the position of its placement class in the <FROM> clause list of classes.
175Dynamic Storage Tiering
Multiple criteria in file placement policy rule statements