Automated tape caching, Virtual tape replication – Sun Microsystems Virtual Tape Library User Manual
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Key VTL features and options
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VTL User Guide • May 2008
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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:
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