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

Note: Some of the commands have changed or removed between the 4.1 release
and the 5.0 release to make placement policy management more user-friendly.
The following commands have been removed: fsrpadm, fsmove, and fssweep. The
output of the queryfile, queryfs, and list options of the fsapadm command now
print the allocation order by name instead of number.
DST allows administrators of multi-volume VxFS file systems to manage the
placement of files on individual volumes in a volume set by defining placement
policies that control both initial file location and the circumstances under which
existing files are relocated. These placement policies cause the files to which they
apply to be created and extended on specific subsets of a file system's volume set,
known as placement classes. The files are relocated to volumes in other placement
classes when they meet the specified naming, timing, access rate, and storage
capacity-related conditions.
You make a VxVM volume part of a placement class by associating a volume tag
with it. For file placement purposes, VxFS treats all of the volumes in a placement
class as equivalent, and balances space allocation across them. A volume may
have more than one tag associated with it. If a volume has multiple tags, the
volume belongs to multiple placement classes and is subject to allocation and
relocation policies that relate to any of the placement classes. Multiple tagging
should be used carefully.
VxFS imposes no capacity, performance, availability, or other constraints on
placement classes. Any volume may be added to any placement class, no matter
what type the volume has nor what types other volumes in the class have. However,
a good practice is to place volumes of similar I/O performance and availability in
the same placement class.
Note: Dynamic Storage Tiering is a licensed feature. You must purchase a separate
license key for DST to operate. See the Veritas Storage Foundation Release Notes.
The Using Dynamic Storage Tiering Symantec Yellow Book provides additional
information regarding the Dynamic Storage Tiering feature, including the value
of DST and best practices for using DST. You can download Using Dynamic Storage
Tiering from the following webpage:
http://www.symantec.com/enterprise/yellowbooks/index.jsp
Placement classes
A placement class is a Dynamic Storage Tiering attribute of a given volume in a
volume set of a multi-volume file system. This attribute is a character string, and
Dynamic Storage Tiering
Placement classes
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