Tech Tips: Sage Advice From Storage Consultants

  1. Take a top-down approach. "Most disk purchases are still done at the group level—and that's the problem," says Mark Roberts, principal at storage consultancy Dataphile Consulting in Austin, Texas. Adding today's high-capacity disks to individual servers creates much unused storage capacity that could be more efficiently allocated through a network-attached storage (NAS) device that serves multiple groups.
  2. Am I really using what I have? Make sure the storage you already have is utilized properly. "We find utilization rates on the high side of 50%, [but] normally it's somewhere in the mid-30s," says James Bowler, a partner in Accenture Ltd.'s Core Technology Practice in New York. With storage prices dropping at a rate of 20% per year, why buy it now if you don't need it?
  3. What is the impact on my IT infrastructure? "Will this technology be disruptive? NAS will tax your topology, particularly if you have a lot of data transfer," Bowler says.
  4. Don't catch "featureitis." Diving too low into features and functions is a trap, consultants say. Stay focused on your needs rather than on "disease-of-the-week technology," says Jon Toigo, a storage consultant in the Tampa Bay area.
  5. Pay attention to performance. "A lot of server-attached storage still outperforms NAS," warns Toigo. Don't trust vendor results. Test an NAS server with your application, and consult peers before buying. You can also download independent test suites and results from Standard Performance Evaluation Corp. But don't obsess, advises Bowler. Speeds and feeds considerations are a hurdle—but it should never be the endgame in choosing a product.
  6. Mind the manageability. "Select your management method, and then select your hardware with management clearly in mind," Toigo says. Better products will plug into your BMC Patrol or Unicenter TNG enterprise management system and work with your backup systems.

Q&A With Jon Toigo: Why NAS Rules

Computerworld recently spoke with Jon Toigo, a storage consultant and author in the Tampa Bay area, to discuss the benefits of network-attached storage (NAS) vs. storage-attached networks (SAN) and where he thinks the technology is headed.

Jon Toigo, a storage consultant and author
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Jon Toigo, a storage consultant and author

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Q: Why choose NAS?

A:
It works. It's a technology that returns the value of the investment—something that's hard to demonstrate with a SAN. NAS can reduce the costs associated with server-attached storage, facilitate data sharing, and it's a very easy plug-and-play solution, so it reduces the risk of downtime. The only [storage networking] product anywhere near developed is NAS.


Q: Are you saying SANs aren't developed?

A:
There is no network storage. Today, we've got thin-server-attached storage—that's NAS—and current-generation SANs—that's switched, server-attached storage.


The implementation of a SAN has produced something that is not a SAN. The primary reason is that Fibre Channel—a serial interconnect for storage conceived as a replacement for SCSI—is not a network but a storage interconnection. It is a server-attached solution with a switch in the middle. You cannot manage it in-band; you have to run another network around to each device. So you have an in-band network doing the data transport, and an out-of-band network doing the control and management and security because they're not in the Fibre Channel protocol.


I'm very bullish on the real SAN ... but that's still many, many years away. We haven't begun to write the software that's required to deliver the value proposition of a SAN. You do not have scalability without disruption. You do not have heterogeneous capability.


Q: Name one NAS advantage.

A:
Dynamically scalable volumes. The server doesn't have any idea how large the volume is, so if you add capacity, the next time [the server software] identifies it as a larger volume. It surmounts problems in server-attached or SAN [storage], where a server tries to own the storage.


Q: Microsoft Corp. says it won't support NAS devices, such as those from Sunnyvale, Calif.-based Network Appliance, yet many people implement them anyway. Why?

A:
Microsoft will only specify that they support XYZ vendor's products, but everyone knows that NetApp is a very good platform. A guy I know from EarthLink said he wouldn't even deploy Exchange without NetApp.


It offers a point-in-time recovery solution, and that's very important to an e-mail administrator with a product like Exchange that has a reputation for dying on you unexpectedly and on a regular basis. The NAS is ideally suited to the deficiencies of the application itself.


Q: Why not NAS?

A:
Most NAS products are suited to file but not block-level storage. Certain transaction-processing applications aren't well served on a NAS box. But that's changing.


Q: What's next?

A:
We need to see a hybridization of SAN and NAS to combine the things that SANs can deliver, which is scalability ... and to centralize management. I see a lot of promise in SAN/NAS hybrids ... a NAS front end with a SAN back end.


The Fibre Channel Industry Association is working hard to add fabric services to the Fibre Channel protocol. But it remains to be seen whether they will have any more success in adding that to a serial interconnect than the iSCSI guys will have trying to get the network to act as a storage interconnect.


Toigo, author of The Holy Grail of Data Storage Management (Prentice Hall, 1999), can be reached at jtoigo@intnet.net or by visiting Toigo Productions Web site.


For more on how iSCSI and IP SANs will change storage-area networking, see the Emerging Technologies story "Get Ready For IP SANs".


Network-Attached Storage Resources


General Information and White Papers


  • Storage Search includes a detailed listing of vendors offering network-attached storage (NAS) products.

  • This white paper (download PDF) describes HighRoad, EMC Corp.'s mechanism for allowing file-level (meaning NAS) access to Fibre Channel-attached storage.

  • Compaq Computer Corp.'s white paper (download PDF) on its Enterprise Network Storage Architecture initiative contains many storage networking goals that have yet to be fulfilled.

  • Download these independently developed benchmark tests or examine the results for NAS products. Warrington, Va.-based Standard Performance Evaluation Corp.'s mission is "to establish, maintain and endorse a standardized set of relevant benchmarks and metrics for performance evaluation of modern computer systems." The benchmarks are considered to be more reliable than those offered by NAS vendors for their products.

  • Visit the NDMP initiative's Web site for details on the Network Data Management Protocol (NDMP), an industry-sponsored open standard for backing up NAS devices.


Vendors Offering Disk-to-Disk Backup Appliances


NAS Server Vendors














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