Saturday, April 20, 2024

Is Going with a SAN Always a Smart Choice?

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A Storage Area Network (SAN) is seen as the way to go in an enterprise of any size. That idea has caught on so strongly that even small businesses now are being wooed by the big storage vendors.

A panel at last month’s Storage Networking World, for example, made the case for SANs in small business. One speaker even said that some its Fibre Channel (FC) products were targeted at small companies, calling them inexpensive. Few in the audience bought it.

”I don’t see myself buying a SAN to replace my USB drive any time soon,” quipped one attendee.

The hype has gotten so intense that it’s almost as though anyone sticking to Direct Attached Storage (DAS) must be living in the past. You’d think it was akin to sticking to mules and kerosene lamps in the age of electricity and automobiles. Yet the missionary zeal behind the SAN movement may not always be the most economical route to follow.

Here we look at two organizations that continue to make heavy use of DAS and are happy with it.

”SAN vendors promise that a SAN increases storage utilization, consolidates administration, improves system performance, simplifies allocation and eases capacity expansion,” says Joe Braud, chief IT architect for Virginia Beach, Va.-based Amerigroup Corp., a provider of managed health care services for the public sector. ”The reality is that SANs are complex, have poor interoperability, have inflexible deployment requirements and are extremely expensive.”

While Amerigroup does use SAN and storage virtualization technology extensively, he continues to utilize DAS at his disaster recovery (DR) site. Instead of installing a costly FC infrastructure and then having to match EMC arrays between his primary data center and DR site, he is content to rely on a simple collection of servers using DAS. To make this work, he also uses DataCore SANsymphony to create a virtualization layer about the SAN and DAS storage hardware.

”We’ve had good success as DAS works fine at the DR site,” says Braud. ”This has saved us a lot of money in back-end FC.”

Continue on to see how DAS fits into the enterprise…

DAS in the Enterprise

While Amerigroup uses DAS on a small scale to cut costs, The Target Companies have gone whole hog.

Target consists of two distinct companies — Target Software Inc. (TSI) and Target Analysis Group (TAG). TSI sells ”Team Approach”, a donor management application for global not-for-profit organizations. Customers include American Diabetes Association, Special Olympics International, and the Nature Conservancy. TAG provides data intensive benchmarking and analytics to non-profits and universities.

Two years ago, an average client install was on at least one eight-way processor Sun or HP-UX database server with more than 1 TB and 100 to 250 users. Now, most clients want Target to host the software.

”We went from 1 TB to over 20 TB due to hosting applications for clients,” says
Drew Farris, CIO of Target Companies.

The company now has its own Oracle 9i deployment to cope with the load. Every hosted database is backed up to a mountable image on a spare server. The IT infrastructure also includes Oracle Financials and Exchange Server. All together, about 30 application servers are used, accounting for about 500 GB of storage.

The storage landscape consists of 50 percent Windows 2000 Servers riding on either Dell or HP, 40 percent Sun Solaris SPARC servers and 10 percent DEC and HP servers. Interestingly, all of this storage is direct attached, either using fiber or SCSI interfaces. A small amount of Serial ATA also is used.

TSI has 20 TB of Sun storage in various configurations: 20 Sun A1000s with 12 36GB drives each; two Sun A3500s with 60 x 18 GB drives each; and six Sun A5200s with 22 X 73 GB drives each. TAG, on the other hand, uses 20 TB of Dell storage, primarily in SCSI arrays. The drive range varies from 18 GB to 250 GB. These arrays typically hold 14 drives.

Cost wise, Farris says Sun-based DAS works out cheaper overall than Dell. ”We’ve purchased all Sun storage for an average of around $7.75 per GB,” said Farris. ”This ranges from $4 to $11 per GB.”

Costs were kept low by purchasing much of the equipment directly from Sun and negotiating a rate well below list price. He outlines several key sourcing strategies to keep costs down:

  • Purchase equipment that is not necessarily the latest generation;
  • Utilize Sun auctions, which provide new equipment at substantial discounts, complete with all licensing and support options;
  • and use the secondary market for such things as bulk packages of new drives.

    Following these practices, Farris says he has paid $175,000 for equipment with a list price of more than $1 million.

    Dell equipment, however, was more expensive when sticking to DAS. Farris’ figures show the average cost of a single-channel Dell 14-bay SCSI array with 73 GB drives to be $13.75 per GB.

    ”This is about twice the cost of redundant dual FC Sun hardware,” he notes.

    He complains that SCSI adapters can exceed $1,400 each and have to be purchased directly from Dell. Further, any replacement parts are refurbished, he adds.

    How does this compare to SAN? When Target Companies contacted analysts to get the low-down on SANs, they were surprised to discover that Forrester Research analysts won’t even address direct-attached storage strategies, and they insist that all storage should be SAN due to the savings resulting from simplified management.

    One Forrester analyst quoted $40,000 per TB as the price of SAN.

    Farris reports, however, that it would cost more than $1 million just to move core databases to SAN. And that doesn’t include the cost of managing the rest of his storage, and the additional skill sets required to deal with a SAN.

    Not surprisingly, he decided to remain a DAS shop.

    Farris admits, though, that there are definite tradeoffs in sticking with direct attached. He has lots of disk drives that have to be serviced and managed, and that means a lot of manual work.

    ”SANs automatically manages free space, optimizes data locations, and does performance tuning,” says Farris. ”Perhaps the worst thing, though, is that if you stay on DAS you can’t brag about the speed of your SAN at cocktail parties.”

    But despite all of this, Farris says he may yet cave in and switch to a SAN. He’ll only do it, however, if the price point continues to decline and SAN management software actually delivers on its promise of simplicity and interoperability at a reasonable cost.

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