While the costs to set up a Storage Area Network (SAN) may seem
daunting to many Internet ventures, the potential benefits it can
provide may well justify the additional expense
Setting up an Internet business in these uncertain times is a
risky business indeed. When entrepreneurs are seeking funding for
proposed ventures through a game show, it's quite obvious that
things aren't at all rosy in the garden of e-commerce. While
venture capital firms may now be weeding out the poorer web ideas
that are presented to them - although certainly not all - it is
also a lot harder for those with genuinely good business
propositions to get the backing they need. Following the stock
market crash of Internet firms after lastminute.com's IPO and the
collapse of ventures such as boo.com, investors have become a great
deal more wary of what they are getting themselves into.
Almost the same situation can be said of established companies
looking to introduce or expand an e-commerce side to their
business. Every aspect of an Internet business is undertaken with a
lot more consideration nowadays, unlike the heady days of
e-commerce only a few months back, when the only aim was to get out
into the market and recognised.Whether you are a start-up or an
established company with an Internet division, it is almost certain
that the funding you are looking for will be far more difficult to
come by, and when it does it could well be far below the amount
desired. In these situations you are going to have to make every
penny count, meaning that you will need to look for a cheap and
easily manageable way to set up your infrastructure.Similarly, the
rise of an Internet company can be meteoric or non-existent. If a
site becomes well respected and popular, the number of requests it
receives per day can increase by several factors in a very short
space of time. In order to handle this, a firm's web infrastructure
needs to be highly scalable, starting perhaps quite small but being
able to expand quite quickly. This needs to be done while making
the most of the technology that is currently in the set-up. A
wholesale reconstruction of the infrastructure every time the
number of hits increases isn't going to help the cash flow
situation and the downtime this requires will be unpopular with
customers.One area that is often overlooked, in terms of importance
to an e-commerce venture, is the back-up and storage requirements
of the systems involved. While possibly not the most vital cost
component of a website infrastructure, the money involved can
become very significant indeed as the site starts to grow, and
management of all the storage drives required becomes increasingly
vital as the size of the site and relevant data continues to
grow.Traditionally, a site will handle demand through load
balancing techniques. While different users may enter the site
through the same gateway, they may often be diverted via a layer 4
switch to different servers in order to avoid congestion. This way,
it is easy to scale the site in terms of computing power. If the
site needs more CPU cycles, the administrator can simply purchase
the necessary server hardware and deploy it into what is
increasingly becoming a load balancing server farm.In this model it
is also common to be using directly attached storage. This is where
each web server has its own storage device hooked up. The storage
device, whether it be a tape drive, disk system or other, is linked
only to one web server and nothing else. Thus, every time a new web
server is added in this configuration, a storage device will also
need to be added. This set-up poses a number of storage issues.If
there is any change to the web data - whether more is added, pages
are updated or data is removed - each and every storage device will
need the changes implemented on them. This also has to be done in a
manner that ensures that all the web servers are running off
exactly the same data all of the time - not a simple task. There is
also the issue that as the website changes and expands, more
storage space may be needed. Where storage is directly attached in
a load balancing web server farm and the capacity of those servers
is reached, each server will require additional storage deployed to
it. This is both costly, due to additional hardware having to be
bought for each server, and clumsy, with each server having to be
taken down to integrate the extra storage devices. Add to this the
costs of adding extra storage every time a new server needs to be
installed to improve CPU processing power, and what seemed to have
been an easy way to manage the website has become complex and
costly.When looking at alternative topologies to directly attached
storage in a website infrastructure, SANs may not initially seem
like the cheapest and most cost effective way to use the venture
capital provided, and certainly the technology is still relatively
new and therefore not the cheapest. The set up of a Fibre Channel
network dedicated to the company's storage needs however, may be
the ideal topology for companies, such as new web firms, who may
need to expand quickly while fully utilising existing technology.In
a SAN, instead of each web server having its own directly attached
storage device, each web server is linked to a Fibre Channel switch
or hub, which in turn links to a cluster of storage devices. These
storage devices in turn can be JBOD (Just a Bunch of Disks) drives
in an arbitrated loop formation, fibre channel disk arrays or tape
drives attached by a SCSI-FC bridge. While the initial investment
in Fibre Channel storage technology may cost more than directly
attached storage for smallish sites, the benefits of the SAN are
many.The advantages of Fibre Channel itself is that it tries to
bring the best aspects of networking, such as large address space
and scalability, together with the high-speed, low latency and
hardware error detection of I/O channels. It can also allow
multiple protocols, like IP and SCSI, to be used over one
infrastructure. The biggest advantages of all, however, are shown
in the layout of a SAN.Since all servers can, if desired, access
all of the storage devices via the SAN, it is only necessary to
store the data on one storage device. This is, of course, without
taking into account fault tolerance, but even if the data is stored
elsewhere, it is still a great deal more economical that storing
numerous images of the same data on back-up devices attached to
every server. Alongside eliminating unnecessary duplicate images,
it also brings economies of scale by being able to store large
amounts of data on just one device that can be accessed by
everything rather than the many smaller devices in a directly
attached storage topology.SAN also makes the storage element
completely independent from the server part of the network,
allowing servers to be upgraded or added while leaving the storage
untouched. Similarly, storage can be added to the SAN without
interfering with the operation of the web servers. This leads to
minimum downtime and service disruption, a vital area for Internet
companies in this era of continuous availability.As discussed
earlier, scaling up a system with directly attached storage is both
expensive and difficult in terms of interrupting the system. SAN
doesn't suffer from this problem. Storage can simply be added to a
switch without fuss. When the switch is full or the topology
requires a more complex structure, adding another switch is
reasonably straightforward and also has the advantage of increasing
the switching capacity of the SAN without degrading the performance
(something which happens on, say, a loop topology). Because of this
scalability, features such as fault tolerance and hot backup can
also be added with relative ease and so only need to be thought
about when there is sufficient financial incentive to do so.It is
this type of scalability and adaptability that lends itself so well
to Internet ventures, as shown in the last few months. Things can
change so quickly in this fast-paced business - you don't want to
get caught out by a sudden surge in demand requiring a complete
overhaul of your systems just a few months after the last one. Yes,
SAN is new and still developing. Yes, it is rather expensive to
implement initially, but that initial step into the world of SAN
needn't be a large one. In essence, all you need to configure a SAN
are Host Bus Adapters for connecting each server to the SAN, Fibre
Channel storage such as JBOD or Fibre Channel RAID, a SCSI-FC
bridge to allow SCSI storage devices to connect to the SAN and
networking components such as a switch. This could start very small
with perhaps just a couple of host devices connected to one SAN
storage device. From there, how the SAN grows really depends on how
the entire enterprise grows.Of course, SAN may not be right for
every Internet company, and there may be many who just cannot
justify the cost that setting up a SAN will incur. For others
however, who may not have even thought about the possibility
before, a thorough cost-benefit analysis of implementing a SAN may
reveal a few pleasant surprises.
Paul Grant