ALTHOUGH THERE ARE MANY storage projects that you could choose to embark on this year, few have as many options to consider as implementing a storage-area network or network-attached storage. The economic realities of 2009 make this task even more compelling.

If the current data center environment is not yet consolidated and all storage is direct-attached, a fair question is, “Why should I do this?” Harry Montanye, senior storage engineer at storage solutions provider Condre Storage (952/294-4900; www.condrestorage.com), believes that the answers lie in resource optimization, improved data protection, and server virtualization. “With direct-attached storage, all your capacity is on different islands,” he says. The challenge is that if one server is running out of disk space, storage can’t easily be reallocated from another server. Also, data protection on shared storage is greatly improved by offloading the backup process from the servers and backing up the shared storage through another nonproduction server.

“The big driver for implementing a shared storage solution in 2009 has to be server virtualization,” says Montanye. With a shared storage solution, capabilities such as live server migration—the ability to move one virtual machine from one physical host to another—are enabled, which brings tremendous value and flexibility to the enterprise.

SAN Or NAS?

The first challenge is to decide between SAN and NAS. The two are often used interchangeably, but as Stanley Chan, product manager at storage provider Sans Digital (www.sansdigital.com), clarifies, “In general, a SAN refers to block-based storage, meaning that it is presented to a server almost as if you were installing a local hard drive.” As a result, you can format it and load the file system of your choice. Chan describes NAS as “an appliance that presents a file system to the server or user, essentially a highly optimized file server.”

Many IT professionals will try to make deciding between a SAN or NAS their first step in the decision-making process. Narayan Venkat, the vice president of marketing at Campbell, Calif.,-based storage solutions provider ONStor (www.onstor.com), believes that it is no longer an either/or choice. “There are solutions available today that can add NAS services to an existing Fibre Channel SAN,” Venkat says. Customers can buy the SAN solution that best fits their needs and can at the same time have the freedom to select the best-of-breed product for file servers. “In fact, many of the NAS solutions today can also provide iSCSI access to the storage,” allowing it to be part of the overall process, continues Venkat.

Network-Attached Storage

For traditional NAS services, look for systems that can support both CIFS (Common Internet File System) and NFS. Additionally, Venkat advises that CIFS support be carefully examined, as “some NAS solutions lack full support of Windows files, and it can cause problems or compromises as the implementation grows. On the other hand, even if the environment is all Windows today, NFS is becoming increasingly critical as Linux becomes more prevalent and with VMware support of NFS as a way to host virtual machine images.”

NAS-based systems are easy to install, and their day-to-day operations do not require much system administrator involvement. File data in most data centers is the fastest-growing data set, and the role of NAS-mounted storage is evolving beyond the file servers used.

Storage-Area Network

For applications that do not support network mounting or where performance is a key requirement, a block-based SAN is a typical solution. Today, the choice in block storage is between iSCSI and Fibre Channel. Both are block-based protocols, but the primary differentiator is that iSCSI runs across an IP network. This brings a familiarity to iSCSI that many first-time SAN customers are more comfortable with.

iSCSI can run on existing 1GbE cards or can use specialized cards called HBAs to do the iSCSI work. “For most customers, the added expense of an iSCSI is [that] an HBA is no longer needed because [of] the processing power available today in the modern server,” says Chan. Montanye adds that the primary use of iSCSI HBAs is typically for being able to boot directly off of shared storage, which a software initiator cannot do. “This is especially prevalent in a VMware environment, where they want to boot the ESX server off the iSCSI SAN.”

Don’t rule out Fibre Channel protocol; its use has become greatly simplified over the past few years, and Montanye says that when performance is needed, he points customers in that direction.

Planning & Implementation

After selection of the type of shared storage and what protocol will be used, the next step in the consolidation project is to identify which servers are going to go on the shared storage. For example, if the primary motivation is to get the live migration benefits of server virtualization, then special care must be taken to make sure that each of the physical server hosts can access the same virtual images.

Proper upfront planning of which servers are going to access the storage and how much each server will need is critical to a successful install. The planning will not only save time at implementation but will also save upfront costs. There may not be a need to purchase as much capacity as is represented by the direct-attached storage. Calculate the amount of storage that is actually in use and what a modest growth rate will be and then purchase just that amount.

One of the other advantages to most shared storage solutions is their ability to add capacity and expand storage pools dynamically, which means that storage can be purchased as a “just in time” inventory item. There is no sense in having it sit unused, as storage gets less expensive the longer you wait.

After selecting the solution and planning the migration, the actual implementation of a modest shared storage solution should be a two- to three-day implementation, including training time. Costs of SME SAN solutions vary based on capacity and type but are often in the $20,000 to $40,000 range.

by George Crump