Recently, I wrote an iSCSI primer
to kick off a series of articles on how to create an inexpensive iSCSI-based
SAN. On such a system, you could conceivably add a ton of fairly inexpensive
disk space, add software that turns a server into an iSCSI target, and create a
relatively cheap SAN. With this block-based storage device, you can store
information, such as Exchange databases, that work better using the block storage
mechanism offered by SANs. In this article, I will cover hardware suggestions
for both a pretty cheap solution and a slightly more expensive, but more stable
solution. In future installments, I’ll discuss (1) Linux targets: Installing
and configuring software to turn a typical Linux system into an iSCSI workhorse
and (2) Windows targets: The same task, but for Windows systems.

Note on terminology

Keep in mind that “iSCSI target” means the server
which you plan to use for your centralized storage.

Disclaimer

I’m not recommending that you run large data centers with
mission-critical applications using these guidelines. This article is aimed at
the smaller IT shop with a limited
budget and at IT shops that need to quickly and cheaply demonstrate a
proof-of-concept iSCSI project. I decided to cover this subject separately in
order to demonstrate just how cheaply and easily you can jump on the iSCSI
bandwagon.

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System recommendations

Before I get into building a system, keep in mind that
“cheap” doesn’t need to equate to “junk”. In fact, you can
build a pretty decent system with loads of disk space for relatively little
money. Or, you can go the slightly more expensive route and buy some prebuilt hardware.
I’ll go over both options in this article.

Regardless of which route you decide to go, there are a few
factors to keep in mind:

  • RAID
    is a must: Especially if you decide to use your cheap SAN in any kind of
    production capacity, you need to protect yourself from failure by—at a
    minimum, using something like RAID 5. Even for a proof-of-concept, use
    RAID to more fully demonstrate what you want to accomplish.
  • With a
    SAN, the number of disks can have an effect on the overall performance of
    the system. Each disk (called a spindle
    in storage speak) can add performance to the system since it adds an
    additional piece of hardware across which data can be striped.
  • As
    usual, RAM and processor speed also play a role in your building process.
  • Since
    iSCSI is heavily dependent on the network in order to work its magic, don’t
    use anything less than a gigabit Ethernet adapter for your storage needs. Better
    yet, bond multiple Ethernet adapters together for additional bandwidth and
    redundancy. For this hardware specification, I’ll specify a single
    Ethernet adapter for the build-to-order system.

Build-to-order

I’m not going to go into a blow-by-blow of the exact
hardware you can use to build your iSCSI target server, except to say that you
need a RAID card and as many disks as you can afford. You can probably spend
less than $700 on a system with a decent motherboard, 2 GB RAM, a reasonably
fast processor, a CD-ROM drive, a gigabit Ethernet adapter, and a case and
power supply that can accommodate many disks.

As for RAID, consider a product such as Adaptec’s
Serial ATA RAID 2810SA
, an 8-port Serial ATA controller that runs around
$400. Combine that with about four Western Digital Caviar SE drives, each with
320-GB capacity and 8-MB cache and running at 7,200 RPM. These drives are about
$175, for a total of $700.

Between the system, the RAID controller, and eight drives,
you could have an iSCSI SAN with close to 1 TB of capacity for approximately
$1,800, and you will leave yourself with some room to add up to four more disks
on the same controller.

Ready-made

You can purchase a powerful ready-made system from a vendor,
such as Dell, for surprisingly little money—if you’re willing to buy
refurbished gear. I’ve selected Dell for this example since you can easily get
to their outlet store and get like-new
equipment for a steal.

If you plan to roll out a production iSCSI target using the
method in this article, you can pick up a refurbished Dell PowerEdge 2850
server with 2 GB RAM, dual gigabit Ethernet, and RAID for around $2,000. You
can also buy a refurbished PowerVault 221S disk array with four 300-GB disks
(providing just under a terabyte of storage after RAID 5 overhead is counted)
for around $3,000. With just four disk slots occupied, that leaves you with ten
more empty slots and a total potential capacity of just under 4 TB in a single array.
Just make sure your system has an external RAID connector for your array. The total
price: $5,000, with room for a ton of expansion. It’s not the cheapest solution
on the block, but it’s certainly less expensive than a lot of options on the
market right now.

The network equipment

You should probably pay attention to this area since iSCSI
can be made or broken depending on what you choose. For this, make sure to get
a gigabit Ethernet switch (or two if you want redundancy; in which case, you
also need two gigabit Ethernet adapters in your server) that supports jumbo
frames, a feature that moves Ethernet around the network using a much larger
than normal frame size of 9,000 bytes vs. the normal 1,500 bytes. This larger
frame size allows iSCSI traffic to move about the network using fewer frames,
resulting in less overhead and better overall performance. You’ll also need to
make sure that the network cards in your server can support jumbo frames. If
you pick a mainstream server system, this won’t be a problem.

If you’re planning to implement a small iSCSI network, you
could use something like the 8-port SMC 8508T switch, which provides gigabit
Ethernet speeds as well as jumbo frame support for a price of less than $100
each. Of course, this is for only 8 ports, so expansion is very limited, but
$100 is a great price for a switch like this that supports jumbo frames.

For higher-end or larger applications, consider a 24- or
48-port gigabit Ethernet switch, such as the HP ProCurve
2824
(a 24-port switch) or the 2848 (a 48-port switch). Both offer jumbo
frame support and are excellent units. The 2824 runs about $1,800 while the
2848 costs a little over $3,000. Bear in mind that, for redundancy, you’ll need
two switches. This part could easily cost more than the server you use for
storage!

Odds and ends

In a powerhouse data center, would I recommend this approach
for building a SAN? No way. But what about for a testing and
development lab?Definitely. For a small
network for which reliable backups are made every night, would I recommend
these hardware solutions? Probably, but it would depend on the application.

I started with this part to demonstrate that the hardware
side of iSCSI doesn’t have to cost a fortune. If you want a “real”
iSCSI array from a vendor like EqualLogic, go for it. It costs more, but you
also get complete redundancy and an enterprise-level support agreement to go
along with it, not to mention rock-solid stability. But, if you’re on a tight budget,
or want to develop a proof-of-concept project for your boss about the
technology, just scare up some spare equipment, buy what you need, and then
read the next parts in this series, in which I’ll go over the process of
turning your pile of hardware into a powerful storage array.