Modular vs. Monolithic Storage: The Business Case

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If the devil's in the details, then storage infrastructure acquisition can be a real hell hole, particularly if you want to lease a large monolithic storage array such as EMC's Symmetrix or Hitachi Data Systems' Lightning, says a data center manager at a large public company in Massachusetts.

Leasing storage, as opposed to buying outright, is desirable, because you are always current and you don't have to worry about disposing of the array once its useful life is up. But if you're not careful how you time capacity upgrades, you may end up paying monthly lease payments far in excess of what you had planned on, the user warns.

In his group's case, they're two years into a four-year lease for an EMC Symmetrix frame, and are running out of disk space. EMC is happy to sell them more disk or to buy out their lease in favor of a newer system, but "it will probably cost us less to buy an entirely new system," he says, from a different vendor.

The problem is the coterminus lease, whereby any capacity upgrades to a frame before the lease ends are financed only over the months remaining on the lease. In that case, the further along in the lease you are, the fewer months you will have to finance the upgrade, and the more "your monthly payments will start to look pretty unattractive," says Mike Kahn, managing director at The Clipper Group, technology acquisition consultants in Wellesley, MA.

From a purchasing perspective, the aforementioned data center manager is a big fan of highly modular storage such as EqualLogic's PeerStorage arrays: 2.5TB "bricks" that contain both disk and CPU, and can be clustered together to create a scalable pool of storage. To upgrade storage capacity, simply add another PeerStorage unit. Because it is leased separately from the original equipment, you avoid the coterminus lease issue.

Because a single PeerStorage array is small, migrating the data off it is easy. Not so with monolithic systems: That "takes a ton of planning," the user says. The time and complexity of migrating data off a monolithic array usually forces customers to bring in a new array well before the old array's lease is up.

Of course, EqualLogic's PeerStorage has its downsides. The user says: "The ATA [disk drive] is a bummer. I'd like to see one with Fibre Channel drives." Furthermore, it's an iSCSI array, and "because of TCP/IP's vulnerabilities, I'm limited as to where I can put it." Nor does it have some of the advanced feature sets of a high-end array.

But the user's point remains: "Monolithic storage vendors" need to follow storage startups' lead and "start to offer new and innovative ways to acquire and finance storage."

This was first published in August 2004

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