Sun Microsystems Virtual Tape Library manual Automated Tape Caching, Virtual tape replication

Key VTL features and options

Automated Tape Caching

The Automated Tape Caching option presents backup applications with virtual tape volumes that are physically implemented on disk, tape, or both. This keeps the implementation simple—the backup application manages only the virtual tape volumes and virtual libraries—while giving the backup administrator the ability to fine tune the physical implementation for best performance and reliability.

VTL software can implement virtual tape volumes and virtual libraries using an optimal combination of resources: disk arrays, physical tapes, physical libraries, and physical tape drives. VTL policies specify where data should reside—on disk for fast random access, on tape for longer term storage, or on both for maximum redundancy—and for how long. Under policy control, VTL software can automatically copy backup sets from disk to tape, outside of the backup window. It can retain the backup sets in the disk cache for a specified period, so that users can rapidly restore data during the period when the need is highest. It can then free up the disk cache for new backup sets while retaining an image on tape. If a restore is necessary, a pointer in the disk cache points the request to the physical tape image, transparently and automatically. The Automated Tape Caching option thus simplifies and automates management of the disk cache, insuring adequate capacity with minimum disk resources.

Policies can be built around the number of days that data sets reside on disk, around a disk‐capacity high water mark, or around a specified event or time of day. Physical tape I/O can thus be run as a background process that does not interfere with production datacenter operations.

Note – Automated Tape Caching and Auto Archive/Replication cannot be used at the same time on the same virtual library.

Virtual tape replication

Replicating data provides additional protection for the information on a virtual tape by maintaining a copy locally or on another VTL server. VTL software supports three replication methods, two of them automatic and one a manual process that can be used if you are not using the automatic methods.

See the following subsections for additional information:

■“Auto Replication” on page 13

■“Replication” on page 13

■“Remote Copy” on page 14.

12 VTL User Guide • May 2008 G • 96267