Fibre channel, the networking technology at the heart of most SANs, is still an evolving standard, says Eugene Sergejew of Unisys.
It consists of a complex combination of parts, each of which has to interact smoothly and faultlessly with each other part. With no clear standard it is often disastrous to pick and choose from components provided by different suppliers.
Paradoxically, for a technology meant to support interacting of heterogenous platforms, SAN does not take smoothly to being heterogeneous within itself.
Users do pick and choose in an attempt to minimise up-front cost, often with predictable negative impact on the total cost and total value of ownership, says Sergejew. “If you pick cheapest component A to go with cheapest component B from a different supplier, you’ll end up with an unsupported system.”
SAN vendors are, however, working to establish a single uniform standard, Sergejew says.
Then there is the question of who to choose as the lead for the implementation. Because storage appears the most important component of the SAN, clients will often choose the storage provider to have overall responsibility for getting the SAN working. This may well be the wrong choice, says Sergejew.
There are few good storage architects in New Zealand capable of planning and implementing the mass of complex interactions, he says. When a storage facility has to have high availability and is mission-critical to the user organisation, “you need strong change control”.
Unisys has a number of SANs in its organisation. Its choice for recent ones adopts the philosophy of uniformity, choosing all the components from one supplier. It helps for Unisys to have a strong relationship with SAN vendor EMC. A recently purchased EMC Symmetrix SAN proved trouble-free in setting up, he says, “but that’s not true of all of them”.
One supplier will have chosen all components and verified their interactions to “best practice” standard, he says. “If a disk dies [on Unisys’s Symmetrix SAN] the machine phones EMC and they just send someone out with a new disk unit, which plugs straight in. It certainly lives up to expectations.”
Unisys found SAN to be an appropriate solution for the mixture of platforms in its Kapiti data centre for the “usual reasons”, says Sergejew. “It’s the acronym Sami — scalability, availability, manageability, interoperability.”
Storage needs at Unisys were growing rapidly — but only to an industry-average rate; the current compound annual growth rate for storage in New Zealand parallels that in the US — 65% or more. The easiest way to satisfy that growth is to add more servers, each with its individually attached storage. However, few businesses can manage that kind of growth with less than a 25% CAGR in server numbers, added to attendant management problems. “You can’t keep throwing administration support staff and maintenance engineers into this mushrooming cloud,” he says.
By consolidating storage, “you don’t run out of slots in your servers, you can easily expand to whatever you need, and it’s easy to monitor [storage growth] trends and usage-growth centrally.”
Much of the growth is “organic,” says Sergejew, simply resulting from expanding business, but is also caused by the adoption of new technologies — “the internet, email, workflow, imaging and CRM are all large consumers of storage.”
For management on the Symmetrix SAN, Unisys uses EMC’s Control Centre software. Some smaller SANs in the organisation use Clariion Navisphere or Veritas’s SAN Point Control.
NAS (network attached storage) is a credible alternative to SAN but only for some kinds of storage need, he says. IDC reports the NAS market is about half the size of SAN although the two technologies are becoming harder to distinguish. Products like EMC’s — formerly Data General’s Clariion IP4700 — behave as SAN or NAS, depending on which front end is attached.
While fibre-channel SAN is still settling, other alternative technologies such as Infiniband are springing up, favouring IP as a transfer protocol. The trade association devoted to developing and pushing the Infiniband standard includes Compaq, Dell, Hewlett-Packard, IBM, Intel, Microsoft and Sun.