Enterprise Storage: Beat the Heat in the Storage Pool

SANs aren't yet the perfect solution to burgeoning data and shrinking backup windows, but products are starting to show promise.

• 07/01/2001

Summertime ... imagine kicking back by the pool, basking in the bright sunshine. Now, say you could turn on the kitchen tap to obtain a glass of glacier-cold water, a brisk tumbler of tea or lemonade - or perhaps even a mug of icy beer or a piña colada. If you have an engineering bent, you might begin to plan a Rube Goldberg contraption with an assortment of pipes and hoses that open and close through a set of valves that allow different ingredients, in measured proportions, to flow into the glass. You could even add a pre-flow quality control to flush out the lines, preventing one drink from tasting like another, and a security mechanism to keep the kids from pouring themselves alcoholic beverages.

Sounds far-fetched, you say? Well, it is, and it isn't. The concept is similar to what we've been seeking from storage area networks (SANs) since the idea was first articulated in the late 1990s.

SANs were originally conceived as an intelligent storage pool or utility, capable of delivering different "flavors" of storage to users and applications on demand. If a user needed to make a file, storage blocks would be organized and presented for use in accordance with the user's file system of choice. If a database application needed a certain amount of RAID 0 storage, a certain amount of RAID 3 storage and a certain amount of RAID 5 storage, the SAN would correctly interpret the requirements and provide the right mix of RAID levels in the right capacities.

The intelligence of current SANs is, of course, not capable of delivering on this vision. Developers are still working just to get the plumbing up and running between the storage devices, switches and servers. Eventually, however, say the SAN solutioneers, it will happen.

They note that the first hurdle - getting reluctant server vendors to buy into a topology that effectively untethers storage from the server (thereby substantially reducing margins on server sales) - has been cleared. In reality, vendor acceptance of this strategy wasn't much of a hurdle, since a growing number of customers needed to scale storage outside the server or array cabinet without so much as an hour's downtime. The handwriting was already on the wall - even before the rise of the Internet - that networked storage was necessary to meet customer requirements.

Those with SAN solutions accept this point, but add that server vendors like IBM and Sun have begun to show a greater willingness to break with their initial strategy of approving SANs only if all components wore the company logo. Early homogeneous SANs are beginning to give way to heterogeneous SANs, they note, with vendors accepting the presence of a competitor's equipment in "their" SAN and stating publicly that they will offer greater support for these mixed marriages in the future. This newfound amicability is also a no-brainer, since heterogeneous configurations were already a fact of life by the time server vendors began to articulate their approval.

On the other side of the switch, SAN advocates quickly add, storage array vendors like EMC have also begun to agree - grudgingly to be sure - to allow their products to be fielded in the same SAN as those of competitors. This is not to say that they accept turning their products into commodities, or are willing to admit that Joe's JBODs and EMC Symmetrix offer anything even close to the same value.

Most array vendors, including EMC, still require that their software be used to "organize and manage" the storage complex. Of course, EMC wraps its self-interest in kinder, gentler terms. Company representatives argue that most heterogeneous SANs show high levels of instability. Storage devices in heterogeneous SANs seem to have minds of their own - appearing and disappearing at random. Since EMC backs whatever it sells - owning the problems that are manifested, as well as the credit for any benefits that are realized - the company must rigorously test the heterogeneous configuration, rooting out the causes of instability, before it approves the configuration for deployment by customers.

Server and storage vendors point accusing fingers toward "the usual suspects" to explain the instability of the heterogeneous SAN: management software vendors, switch manufacturers, the Fibre Channel protocol itself or implementations made of Fibre Channel by host bus adapter vendors or controller manufacturers.

There is considerable blame to go around. The fact is that SAN management, which should have been a prerequisite for storage pools, is only now beginning to capture the mindshare of SAN vendors and consumers.

Unfortunately, the SAN storage pool is still not necessarily the best way to beat the heat caused by burgeoning data and shrinking backup windows, but management tools are showing signs of improvement. Even so, in the absence of the intelligence promised long ago by those with SAN solutions, we're still required to mix our own drinks.

It may be for the best, in any case. Recent history teaches us that efforts to develop multi-purpose, one-size-fits-all, Swiss Army Knife-type solutions - from WAP phones to SANs - tend to yield expensive products that perform no single task to anyone's complete satisfaction.

An alternative to SAN pools is emerging around the network-attached storage model, however. NAS-SAN hybrids and clustered storage solutions may soon provide highly manageable, but application-centric, storage solutions that enable IT managers to beat the heat without taking a bath.