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About Dynamic Storage Tiering

VxFS utilizes multi-tier online storage via the Dynamic Storage Tiering (DST) feature, which functions on top of support for multi-volume file systems. Multi-volume file systems are file systems that occupy two or more virtual volumes. The collection of volumes is known as a volume set, and is made up of disks or disk array LUNs belonging to a single VxVM disk group. A multi-volume file system presents a single name space, making the existence of multiple volumes transparent to users and applications. Each volume retains a separate identity for administrative purposes, making it possible to control the locations to which individual files are directed.

See Multi-volume file systems.

  Note   Some of the CLIs have changed between the 4.1 release and the 5.0 release. These changes make policy management more user-friendly. The following are the CLIs that have changed: ...

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.