Organizations are clamoring for better ways to serve up files to meet the insatiable demands of applications and network users. Traditional file server computers are far too small for many modern businesses, and large
storage area networks
(SAN) are often too expensive and complex.
Network attached storage
(NAS) technology has filled this gap, providing powerful file serving capability with huge storage capacity and an increasingly comprehensive suite of enterprise-class features. NAS has emerged as a primary storage resource in the small and midsized business (SMB) and has proven itself in the enterprise. "I would say that every one of those [Fortune 100 or Fortune 200] companies has some form of NAS file sharing -- whether it's an appliance or Windows file serving in their organization," says Greg Schulz, founder and senior analyst at the StorageIO Group in Stillwater, Minn. This article covers the essential concepts of NAS, highlights key implementation issues, shares some real-life NAS case studies and looks ahead at the future of this technology.
In its simplest form, NAS is a disk-based storage system with an IP network interface that is designed expressly to serve files on an IP network. This dedicated file serving offers vastly greater storage capacity than traditional file server computers that typically hold just a few disks. NAS is also noted for its superior connectivity and storage performance, allowing applications and users to be serviced faster and more reliably than common file servers can handle. NAS is recognized for three principal benefits: consolidation, deployment simplicity and ease of management.
Before NAS, there might have been hundreds or even thousands of individual file server computers scattered throughout an enterprise -- each with a few disks, and each demanding maintenance or configuration from IT staff. Today, a NAS system can replace a huge array of file servers, @32605 consolidating terabytes (TB) of storage into a single system at one location. A NAS is also simple to deploy, usually requiring little more than a power source and an IP network connection for basic operation. A proprietary operating system is frequently included to enhance performance and ensure security.
is a common feature for data protection, and some NAS systems now support dual-parity RAID (RAID-6 or RAID-DP) to guard low-cost
storage against multiple simultaneous disk failures. More disks can easily be installed to add storage capacity, and if the NAS box fills to capacity, a new NAS box can be purchased and connected with equal ease. Finally, the consolidation and management of NAS resources can typically be managed through a single management software tool. Often, the management software can support multiple heterogeneous storage systems, easing management overhead even further.
NAS has evolved along with
SANs, and the two technologies appear to have divided into separate storage camps. NAS has typically taken on the role of low-end storage, while Fibre Channel SANs have been associated with high-end performance. While this may have been a justifiable segregation in years past, industry experts say that faster Ethernet and better NAS system designs are changing this relationship. "Historically, there's been some cost advantages to NAS, which has inadvertently pigeonholed NAS to be perceived as cheap 'toy' storage -- not befitting an enterprise," Schulz says, noting that contemporary NAS systems can support the storage tiering, high performance and high availability that had only been available in SANs.
Although we often refer to NAS as a dedicated appliance (e.g., a NAS box) with its own internal storage, some organizations may choose to forego a new appliance when a SAN already exists in the enterprise. Rather than a NAS appliance, a NAS gateway can be used to serve files from SAN or some other external storage. The presence of a gateway adds NAS functionality, but uses the SAN or separately attached disk array for actual storage. The advantage of a gateway is that NAS storage is not limited by the capacity of the appliance itself, but rather by the storage capacity of the separate array or SAN, which can be considerably larger. For more details on NAS appliances and gateways, see the
NAS Upgrades Buying Guide
Today, experts agree that NAS has earned a permanent place in the enterprise alongside the SAN. SANs remain the preferred choice for block-based storage, but NAS has become a staple of file storage, especially in its ability to serve unstructured file data, which is growing rapidly in the enterprise. NAS can easily exist alone, and many smaller organizations that are moving beyond file servers will adopt NAS. But SAN and NAS technologies can also coexist when the storage environment handles a mix of block and file data. "In a large environment, every good SAN should have a NAS -- every good NAS should have a SAN," Schulz says.
NAS implementation typically involves the deployment of an appliance or gateway device, along with the configuration/management software that accompanies it. Experts say that most NAS deployments are turnkey, requiring only simple setups for basic operation. High-end NAS systems can be a bit more complex and generally involve more sophisticated tools, such as backup, replication and snapshot software. Some software may require a separate purchase, so it's important to note what functionality is available out of the box, and which features may require a separate purchase.
Keep an eye on the NAS network traffic. Without adequate bandwidth, a network segment hosting the NAS can easily become overloaded and impair performance. In most cases, a NAS is implemented with multiple
ports that can be aggregated for improved bandwidth. Multiple ports also allow for failover, an essential element of high-availability operation.
Performance is also a serious issue when the NAS is called upon to handle transaction-centric applications, such as databases or email systems like Microsoft Exchange. SANs are still the preferred choice for storage in heavy transactional environments, but high-performance NAS systems are offering alternatives when the application workload can be balanced with the NAS system. "You start to run into limits with NAS at the very high end where you're serving up hundreds or thousands of database transactions per second," says Phil Goodwin, president of Diogenes Analytical Laboratories Inc., noting that very intensive
environments can have trouble being hosted on NAS.
As an added wrinkle, a NAS can sometimes influence software support. For example, some block-based applications may not even support deployment on file-based storage, so be sure to review the applications that you intend to host on NAS and verify that the application vendor will continue to support those applications. Lab testing is an excellent way to see the application's behavior and stability on a NAS prior to a major rollout.
The actual effort needed to manage a NAS is typically not significant, and good tools can ease the overhead. Opt for tools that will support multiple NAS systems and heterogeneous storage systems wherever possible. This will prevent the IT staff from having to deal with multiple management tools as more NAS systems are added. Otherwise, the ease of NAS deployment can eventually result in a myriad of NAS systems and file servers -- the sheer number of NAS systems can ultimately cause management headaches. "In the PC and server world, the solution is some sort of consolidation or virtualization," Schulz says, "and we're going to start seeing more of that [virtualization] in the NAS space."
The impact of NAS
NAS usually helps to overcome the expense of a SAN or the management headaches of DAS. For Jeremy Whaley, director of information systems and network services at Claremont McKenna College in Claremont, Calif., NAS overcame both issues. Several years ago, the college employed an IBM-based SAN with 4.5 TB, with another 3 TB spread out between various DAS systems connected to servers as needed. The expense of server HBAs left the SAN poorly utilized. "Only a handful of Windows file servers were taking advantage of the SAN," Whaley says. SAN performance had also proved to be problematic, and frequent SAN reboots interrupted service to users across the campus.
For Whaley, the challenge was to improve storage performance while keeping costs in line and begin a process of server consolidation that would support more storage on fewer platforms --- while eliminating the security and patch headaches with a proliferation of Windows file servers. The college opted for the simplicity of IP network connectivity. "We knew we needed to fix, replace or redesign the storage facilities for the future," he says. "The reason that we landed on NAS rather than another SAN is because we wanted to actually retire and consolidate our file servers -- of which there were many." After about six months of consideration, the college settled on a BlueArc Corp. Titan NAS system. Whaley notes that BlueArc also supports iSCSI, so there is always a potential to add an iSCSI SAN later if necessary. See the article
for more information.
After installation, SAN data was migrated to the NAS using the Robocopy utility. Testing and final activation took place at the end of December 2006. There were numerous technical issues to resolve with network segmentation, but Whaley reports a problem-free deployment of the NAS itself. Today, the NAS provides 19 TB of usable storage to the college. Retiring individual file servers has considerably reduced server management and maintenance issues, eased network congestion problems, and vastly improved storage reliability. "After we cut over [to the NAS] we continued monitoring the two side by side, and the old SAN has already had three errors where we would have had to schedule maintenance in the evening with IT staff on campus," he says. He also noties that remaining file servers have been very stable.
More storage will undoubtedly be added to the NAS system into the future, but Whaley is also considering a move to virtualize remaining file servers -- further consolidating the infrastructure and management overhead. Beyond that is the prospect of disaster recovery for the college. "This particular NAS device has a really wonderful replication feature built in," Whaley says. "If you have a second unit out there, you can replicate between the two in several different fashions."
Healthcare providers have seen a dramatic increase in their raw storage to meet the demands of digital medical images. The Capital Region Orthopedic Group in Albany, N.Y., struggled with outdated practice management and surgery systems offering about 200 GB of usable storage. With the move to a new facility back in 2000, the adoption of an updated practice management system and a shift from conventional film to digital X-rays in 2003, the group's storage demands exploded. "We went from a mom-and-pop shop to an enterprise almost overnight," says the Group's chief technology officer, Raymond DeCrescente, Jr. The incessant need for storage drove the adoption of a Hewlett-Packard Co. (HP) SAN. An HP b3000 NAS head accesses a current total of 8 TB SAN storage for the group's updated picture archiving and communication system (PACS). Each digital X-ray study requires 25 MB. "We basically are filling our storage now at 5 GB per day," he says.
The choice of vendor came down to a matter of convenience and capability. DeCrescente notes that access to local HP engineers and their ability to redesign a data center from the ground up were critical factors. This single-source approach avoided the need to tackle numerous storage and infrastructure upgrades through separate vendors. DeCrescente is particularly pleased with the scalability of his storage, noting that current 144 GB drives can be upgraded to 300 GB Fibre Channel drives. This essentially doubles the storage to 25 TB. By installing additional drive shelves, the SAN can support over 50 TB. "I'm planning on doing just that, and then I can do
[D2D] snapshots," he says.
It took about a month to test and burn in the new infrastructure, but DeCrescente is pleased with the reliability and call-home capability of the storage. Although he cannot quantify the
return on investment
(ROI) or other financial impact of his storage choices, the benefits are clear. "You can't help but to save time on the maintenance." The one bit of advice DeCrescente offers is to take full advantage of training opportunities. "If I look back on it, I would have done that training during that month while everything was burning in."
After DeCrescente adds storage, he intends to add HP data protector and snapshot software for enterprise-class data protection. A hardware refresh is planned in another several years, which will move the current SAN and servers offsite and install a new HP SAN in the main office -- allowing for D2D disaster recovery.
The future of NAS
Experts agree that NAS has a bright future in all types and sizes of enterprise, noting that NAS technology is evolving to meet more demanding tasks. Traditionally, NAS is deployed to support file-based applications in light-to-moderate traffic storage environments. But today, NAS use is expanding down into the small office/home office (SOHO) and up into the enterprise, and the lines between block and file storage are blurring. More block applications are being deployed on NAS systems where they would have appeared on SANs in the past. NAS systems are also increasingly capable of handling database and other traffic-intensive applications. Such improvements are often matched with better management tools and high-end features, like replication and snapshots. "There are some very large companies that run almost exclusively on NAS," Goodwin says. "I think as it becomes more capable, as people deploy more gateways and provide virtualization to their environment, NAS will continue to expand its presence."
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