Sun Microsystems Virtual Tape Library - Manual (Page 15)

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CHAPTER
1
Introduction: VTL appliances and
enterprise data‐protection
Sun StorageTek VirtualTape Library (VTL) technology makes the benefits of disk‐to‐
disk‐to‐tape architecture available to complex backup environments that cannot
readily accommodate the disruptions and administrative burdens that often
accompany major changes to information‐management environments and processes.
VTL solutions make disk media available to applications that are configured to work
with tape. VTL software presents your existing tape‐centric backup architecture with
what appear to be familiar tape libraries, drives, and data cartridges while managing
the complexities of the implementation—disk arrays, RAID groups, and logical
volumes—internally.
Such transparency is absolutely critical when backup is just one aspect of an
enterprise‐wide business‐continuity plan. When legacy systems and multiple,
interdependent applications, procedures, policies, and/or service providers are
involved, even modest changes to a backup architecture can have unforeseen, far‐
reaching consequences.
The advantages that disk‐to‐disk backup has to offer are no less critical in complex
environments. Heavy workloads, tight schedules, and multiple dependencies often
make backup windows very tight or non‐existent. Jobs that fail to complete cannot,
in most cases, be retried. Tape‐based backup systems perform well when handling
big jobs, like full backups of large files and file systems that can stream large
amounts of sequential data. But much of the current backup workload consists of
intermittent, essentially random I/O—incrementals, full backups of heterogeneous
small servers and workstations, and small files (such as those associated with email
systems). Tape drives perform poorly under these conditions. But disk‐based storage
is ideally placed to handle this type of I/O.
The remainder of this chapter provides:
■
a brief summary of VTL “Features” on page 2
■
a detailed discussion of the “Advantages of VTL tape virtualization” on page 4
■ a more in‐depth look at selected, “Key VTL features and options” on page 8.