New SAN Tape Backup Strategies – Not Just for Early Birds

LAN-free tape backups and server-less back ups have become a key storage
management capability for the early birds building economies of scale (mostly
large organizations) in their storage area networks (SAN). However, the
emergence of low-price tape automation systems could provide similar SAN
backup capabilities to organizations of all sizes.

Working together the SAN backup building blocks – tape drives, tape
automation, interfaces, and software – can enable multiple servers to share
the backup resources and, thereby, the need for disparate backup devices.
The backup takes place as a result of a comprehensive architecture that moves
beyond the traditional LAN-based backup to a LAN-free backup and finally to a
server-less backup.

Tape storage products remain the most effective media alternative for server
and network backup. DLT (digital linear tape) media has become the standard
for medium to high-end server back.

Tape automation products offer the advantage of unattended backup.
Specifically, the backup occurs without any or minimal operator intervention,
and provides days’ worth of backup tapes, which an operator doesn’t have to
store and to retrieve. For example, tape autoloaders provide automated
solutions with one tape drive and up to seven tape cartridges or enough tapes
for a week’s worth of backups without any operator needed to handle any
media.

Higher-end tape libraries contain multiple drives and 100’s to 1,000 of
cartridges. These products typically have had SCSI interfaces, but fibre
channel interfaces suitable for SANs have begun to appear. Software products
round out the complete solution for getting data stored on tape during a
backup or retrieving data from tape for a restore.

In the traditional LAN environment, multiple clients or servers get backed up
to one server that has the tape automation subsystem attached. This
technique provides a central point of control for the backup software, but
has the disadvantage of requiring all data to be passed across a relatively
slow LAN to the one server that is performing the backup.

The first step in the emergence of SAN solutions have eliminated the LAN
bottleneck and provide direct backup from multiple servers to the tape
automation subsystems. This LAN-free backup technique provides multiple
paths into the tape automation systems, typically through a fibre channel hub
or switch.

The final step in the SAN architecture for tape backup eliminates the need to
pass the data from the disk arrays being backup through a server. With
server-less backup, the server issues the backup commands (control path), but
the data path goes directly from the disk subsystem to the tape automation
subsystem. This technique frees up cycles on the server to do productive
processing and simplifies the movement of data.

Several developments have to occur in order for the new SAN backup
architecture to benefit all types of organizations. First, the tape
automation vendors must enable an organization to scale from a starter
autoloader to a larger tape library – one that can handle more drives and
tape cartridges as the organization’s needs grow. At the same time,
low-price tape automation subsystems must be reliable enough to eliminate
operator intervention and to support LAN-free and server-less backup
techniques.

Finally, with the increased acceptance of fibre channel interfaces, tape
automation vendors must migrate their products from the popular SCSI
interface to fibre channel to SCSI bridges, then to integrated fibre channel
controllers in the tape library, and finally to integrated fibre channel
drives within the tape library.

Elizabeth M. Ferrarini – She is a free-lance writer from Boston,
Massachusetts.

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