While SANs can provide a world of benefits, backing up a myriad
of servers to a SAN can be tricky if not approached correctly.
There are a number of missteps you can make in the implementation
or subsequent management of a SAN-centric backup architecture.
Using a tape library and disks as a key component in the SAN can
also complicate matters. Users may find questions arising with the
use of different platforms and operating systems in the SAN backup
process, as well as issues associated with the cost to back up
multiple servers.
Here, SearchStorage.com has collected some of the best advice on
the ins and outs of SAN-based backups. (Do you have other
experiences or gotchas to pass along in our compilation of
SAN-based backup do's and don'ts? Please
let us know, so that
we can pass them along to your peers.)
Table of
Contents
Overview of SAN-based backup techniques and differences
Beating the cost factor of implementing SAN-based backups
Logistics of implementing SAN-based backups
User case studies of SAN-based backup architectures
SAN-based backups supporting multiple operating systems and
platforms
Overview of
SAN-based backup techniques and differences
Five backup options to consider when implementing a SAN/NAS
solution:Part 1,
Part 2.
In this two-part series, Chris Poelker explains some different ways
to use a SAN or NAS subsystem when you are trying to replace tape
as the primary backup medium. Included among these are the use of
offsite mirrors, remote tape backups and snapshots in the local
SAN.
Setting up a centralized backup in a NAS and
SAN
A reader new to the world of networked storage wanted to know SAN
expert Christopher Poelker's advice on the best options for backing
up 10 servers in one locale and 3 in another. In his answer,
Poelker takes an excerpt from Chapter 9 in his book, SANs for
dummies, providing a detailed listing and explanation of the merits
of different backup architectural choices. These include LAN-less
backup to a shared tape library over the SAN, serverless backup to
a shared tape library through the SAN, disk-to-disk backup, image
copy in the SAN and SAN data replication/remote backup.
Working with third party and extended
copy
Chris Poelker explains for one reader the difference between the
use of third-party copy and extended copy (or E-copy, X-Copy) for
backups in a SAN environment.
The difference between LAN-free vs. server-free
backup
In 2002, contributor John Merryman provided a useful overview of
the different implementations of LAN-free vs. server-free backup.
While some information has changed since then, the fundamentals
remain the same. This is a great backgrounder for those new to the
concepts of SAN backup.
Back
to Table of Contents
Beating the cost
factor of implementing SAN-based backups
How to beat the high costs of adding servers to
a SAN
This reader has done his homework and contacted expert Chris
Poelker after he did the math and realized his proposal for a SAN
to consolidate backups in his environment was going to mean a cost
of roughly $8,000 to connect each server to the SAN (in this case,
a Xiotech system). Yikes! While he's still a believer in the merits
of a SAN, he turned to Chris to help him save the ROI in his SAN
proposal from going right out the window. Chris' response? In what
we've dubbed, "The doctor is in: A six-step prescription for SAN
backup," Poelker describes six ways to implement a SAN backup
strategy using as few servers as possible.
Evaluating the costs of a SAN-based backup
strategy
Are you trying to decide whether SAN-based backup is for you? Here,
regular contributor Simon Gordon gives a general definition of
SAN-based backup as it compares to other backup methods: Namely,
direct backup and network backups. He also dissects the capital
costs, operational and soft costs to consider with all three backup
methods.
SAN-based backup considerations as you scale out
your SAN
While expert Chris Poelker shares the conventional wisdom of
setting up a SAN with two host bus adapters (HBAs) per server, he
also cautions that backups present a more complex scenario
involving the need to reduce backup-related bottlenecks. As you
begin to scale your SAN and add more servers per director, backups
can tend to get noticeably slower. While it might be ideal to add a
third HBA per server, it's also a costly proposition. Read some of
Chris' other recommendations for allowing speedier SAN-based backup
at a reasonable cost.
Back
to Table of Contents
Logistics
of implementing SAN-based backups
Running tape and disk down the same
HBAs
One reader was working with an integrator to install and implement
a SAN-based backlup architecture, when he started experiencing
strange tape media errors. He wondered about the need of a third
HBA for backup servers? Chris gets to the crux of the matter by
breaking down the questions you need to answer when you want to
perform backup via SAN: Who's going to do it (production server or
backup server)? How will you mount the LUN to back it up? Will LUN
access be over the network or the SAN? Do you have to back up
offline, or can you do it online?
Why dual fabrics are often the way to go for
SAN-based backup
Chris Poelker describes the four reasons for implementing dual SAN
fabrics on a large-scale SAN. After reading his response to a
reader's question, it's no surprise that he still recommends dual
fabrics for SAN backups, if you don't have sufficient server slots
or budget to implement a third HBA and dedicated backup path within
your SAN.
Words of wisdom for backup/restore in a SAN
environment
Chris Poelker describes for a reader how to do SAN-based backups to
a tape library when the reader's backup server is only connected to
the SAN, not the local area network (LAN). The short answer is that
you can do this in the above scenario, but you'll probably need to
do some fancy footwork with your LUNs and taking snapshots of data
found on the other servers. There are further insights here on
server-free vs. LAN-free backup.
Moving to SAN from several servers tied to DLT
machines
One reader faced a logistics and management nightmare in trying to
maintain the backups between several servers that were tied to
several other DLT machines. Chris Poelker offered six alternatives
to the reader, with one flavor or another of SAN-based backup
appearing several times in the choices.
Ways to make disk and tape play nicely on the
same SAN
While most folks maintain putting disk and tape on the same SAN may
not always work out so well, Chris Poelker believes this is a fine
option, provided you are using Fibre Channel-Arbitrated Loop
(FC-AL) for the SAN fabric, and you put disk and tape on the same
loop. Read what else Chris recommends in this expert answer.
Disk and tape on the same HBA? Think
again.
In this tip, learn why IBM recommends using different HBAs for tape
and disk connectivity and creating a separate zone on the SAN for
the tape.
Backup software optimized for SAN-based
backups
In part 2 of a detailed answer Chris Poelker provided on when a
server is a good candidate for your SAN, he provides a basic list
of the backup software vendors who offer software already optimized
for use with the SAN. These allow you to back up your data directly
from a disk in the SAN to a tape drive, speeding backups.
Back
to Table of Contents
User case studies of
SAN-based backup architectures
Tape SAN gets good rating from credit analytics
company
This case study explores how one credit analytics firm succeeded at
reducing its backup windows substantially through the use of both a
disk- and tape-based storage area network. This is no small feat,
given the fact that the company's storage needs grow on average
between 1-2TB per month.
Storage network centralizes tape
backup
In this case study, learn how the MGM Mirage's IT department went
from a decentralized tape backup operation that spanned five sites
and three continents to one centralized SAN-based backup
methodology. You'll learn here how they decided to grow out their
initial SAN-based architecture in phases, based on the data growth
needs of their enterprise.
Back
to Table of Contents
SAN-based
backups supporting multiple operating systems and platformsHow to perform cross-platform backups to a SAN
tape library
How should you engineer cross-platform backups to a shared SAN tape
library? Or, should you even set it up that way to begin with? This
reader asked expert Chris Poelker if there was any reason for not
sharing AIX, Solaris and NT2000 to the same tape drives in a SAN
fabric as long as they were zoned to see the tape drives but not
each other? Among Poelker's advice here was, "He who controls the
robotics, controls the library." Poelker also discusses the
appropriate use of taking image copies in this scenario.
How to make SAN-based backup work for Macintosh
OS workstations
Chris Poelker tells one reader how the purchase of a data router
(or Fibre-to-SCSI bridge) is all that's needed on the hardware
side, at least, to connect an existing tape library to their new
SAN. However, supporting the software side of SAN-based backups for
Macintosh workstations and servers may take a little more research
to track down the appropriate set of tools.
How to back up Netware systems to the
SAN
While this reader was trying to figure out how to back up his
Netware systems using a Compaq StorageWorks SAN at the time, Chris
Poelker's response still stands the test of time. Included in this
gem is Chris' advice to use SAN-based "clones" of the production
volume for back up to Netware, and to create a mirrorset on the
array you want to be able to back up. Chris goes on to suggest a
couple of CLIscripts for automating the creation (and breaking off)
of a mirrorset.
Do you have questions on SAN-based backups for our networked
storage experts? Ask them
here.