I recently worked with a small business that was looking for
a way to organize the data storage on the network. They had a number of
servers, including two Windows 2000 domain controllers, a terminal server, Web
server, and two dedicated file servers, as well as about 10 workstations. There
was no lack of free disk space on the network; the problem was that it was
spread out all over the network.

I call it the “it just grew that way” syndrome, and I see it
on many small to medium networks when companies start out with just a few
computers and add more as they add employees and/or take on more projects. The
more the company grows, the more scattered the data gets.

It’s much easier to plan a good, scalable data storage
strategy from the beginning. But does this necessarily mean putting all your
eggs (or in this case, all your data) in one basket, or does distributed
storage make more sense? Certainly, having the company’s data in one place
makes it easier to manage, secure and back up. But you’ll want a good fault
tolerance plan to protect against data loss.

There is no “one size fits all” solution — even for all
businesses of the same size. Most companies, once they outgrow the “store it
wherever it happens to fall” stage, move to file servers with some sort of RAID
array. This is the time to plan for anticipated growth.

Planning scalability

When you think of scalability in regards to your RAID
solution, you may think only of storage capacity: can you expand the disk
capacity to meet your future needs? In fact, this is only one aspect of
scalability, but it’s an important one. How many disks can be added to the
array? You can connect up to 15 disks per SCSI channel (SCSI-2). That might
sound like far more than you’ll ever need, but remember that
10 years ago, a one-gigabyte hard disk seemed huge. We didn’t anticipate the
huge video and media files that are commonplace today, and as applications
become more sophisticated, we can’t predict the sizes of the files they will
create.

For greater capacity, consider going with fibre channel
instead of or in addition to SCSI. A fibre channel loop can support 126
devices. Another advantage of fibre channel is that it supports longer cable
distances. As your business grows and you add more devices, you may also need
to spread them out more. Whereas SCSI works best with cables no longer than 3
meters, fibre channel allows for more than 30 meters between devices, and a fibre
channel Storage Area Network (SAN), using dark fibre, can support links of
several kilometers in length.

In selecting a solution, you should consider whether the
hardware vendor has planned ahead to support new, faster, higher capacity disks
in the future. Will new hardware or software be required to use the newer
disks?

The nature of your business may dictate that you need
scalability without downtime, so you’ll want to find out whether disks are “hot
addable”: if you need more capacity, can you add disks to the array without
taking it offline? Not so long ago, adding a disk to an array required backing
up all your data, adding the disk, reformatting the array and then restoring
the data. Most modern RAID solutions provide you with configuration tools for
changing or adding disks dynamically. Again, fibre channel offers advantages
with its better support of hot plugging.

Check out not only whether you can add disks dynamically,
but the configuration in which disks must be added. A SCSI array in which the
data is placed on one disk with parity information spread across five disks
will usually require that you add six disks every time you want to increase
capacity. With fibre channel, arrays can be configured so that you only need to
add one disk at a time.

Fibre channel technology and SANs

Fibre channel technology is the basis for SANs, the next step up in scalable
storage solutions. A SAN is a group of networked storage devices that can be
directly accessed from all of the servers on the network. As your business
grows, speedy access to data becomes more important, and a SAN provides a fast,
switched connection.

Best of all, SANs
can grow with your business and your network. Additional storage devices can be
added to the SAN as the need arises, and with little or no downtime. Additional
servers can be added to support more users (without adding more storage capacity
unless/until it’s needed). Switches can be added to prevent deterioration of
performance as more users and storage devices are added.

A SAN can start out small — just one SAN-attached storage
device and a couple of servers. The SAN configuration can grow as your storage
needs increase. You can attach backup tape devices to the SAN, for faster
backup.

What about Network Attached Storage (NAS)? While a SAN in
essence moves storage to its own network and
eliminates the file server, NAS builds on the file server concept but
simplifies it by removing all the unnecessary functions of the operating
system. A typical file server runs Windows, NetWare or a UNIX/Linux operating
system. This creates extra resource overhead and makes the file server
vulnerable to security breaches and attacks that target that OS. A NAS device
uses a stripped-down OS that makes it more secure and faster than a regular
file server, although it usually uses an Ethernet connection to connect to the
network like the typical file server.

NAS devices are often “turn key”
appliances that are easy to plug in, set up and operate. They are usually less
expensive to implement than SANs.
However, they have traditionally suffered from lower performance and more
limited scalability. Since they are self-contained appliances, it’s been
difficult to add capacity. However, new technologies, such as switching devices
that let you distribute data across multiple NAS devices, are changing this and
the convergence of NAS and SAN is making the former more scalable than ever.

Choosing the right storage solution for your growing
business isn’t a “no brainer.” You have more choices
than ever, and scalability and performance must be weighed against ease of use
and the ever-present budget considerations. But spending a little more now to
plan for future growth can actually save you money in the long run, so take the
time to ask the right questions about scalability when you compare storage
options.