Tape remains the quintessential
backup storage technology for many
organisations, offering relatively low media costs, broad backup
software support, and convenient offsite storage potential for
disaster protection. But picking the best tape library for
enterprise deployment is a serious challenge.
This guide focuses on the specific considerations of
enterprise-class tape libraries. You'll also find a series of
specifications to help make on-the-spot product comparisons between
vendors like Quantum, Hewlett-Packard, IBM, SpectraLogic and
others. Beyond the
essential considerations involved in any backup
product, there are several additional considerations for
enterprise-class tape library systems:
Consider the library capacity for tape drives and tape
media. The Scalar i2000
tape library from Advanced Digital
Information Corporation (ADIC) can support up to 96 LTO-3 tape
drives, and house anywhere from 100 to 3492 tape cartridges,
yielding a total (theoretical) capacity of (3492 x 800
gigabytes) 2,794
terabytes (TB) of compressed data. Libraries
like the PX720 from Quantum Corp., can support a variety of
drive types including SDLT 320, SDLT 600, DLT-S4, LTO-2 and
LTO-3. In most cases, a tape library will not ship fully loaded.
Instead, a library will typically ship with fewer drives, and
the number of tape cartridges will expand over time.
Consider the connectivity options. Many tape libraries
employ FC or SCSI
host bus adapters (HBAs) for connectivity
directly to a
SAN switch. As an example, Qualstar's XLS
includes integrated support for up to four dual-ported HBAs --
eight ports total. Gigabit Ethenet ports may be available for
connection across a
LAN. A standard Ethernet port may allow LAN
connectivity for tape library management applications like
Qualstar's X-Link or the BlueScale Environment with SpectraLogic
Corp., libraries.
Consider data transfer rates between the library and
network. Transfer rates generally limit your backup window. For
example, the XLS product from Qualstar Corp. is available in a
variety of modular configurations touting native data transfer
rates from 1.1 TB/h up to 27.6 TB/h. An enterprise with 10 TB to
backup would then require a nine hour backup window with the 1.1
TB/h configuration, or less than 20 minutes with the 27.6 TB
configuration. Transfer rates are generally influenced by
additional I/O modules installed in expanded library
configurations.
Consider the tape storage environment. When considering a
tape library, be sure to evaluate the long-term internal storage
conditions such as temperature, humidity and contamination. Some
libraries try to optimise tape and drive reliability by introducing
filtered positive air pressure to reduce dust and other
contaminants. If tapes are stored offsite, remember to inspect the
conditions at any remote location as well.