Network-attached storage (NAS) is quietly transitioning from an ad hoc, departmental storage add-on to a serious top-down enterprise storage resource. This highly reliable file server approach has always been relatively inexpensive and easy to configure and manage. But now, a single NAS server accommodates tens of terabytes of data, and NAS systems sport more efficient backup technology and support applications more efficiently over today's faster Gigabit Ethernet networks. What's missing? Better tools to manage across distributed NAS resources.
Bigger and Bigger
As its capacity and scalability increase, NAS is taking on new roles in the enterprise environment.
While storage-area networks (SAN) have been getting all the attention, NAS has been quietly breaking all the rules. Essentially a plug-and-play disk storage subsystem with embedded file-serving software, NAS technology was originally seen as an easy way to add a few hundred gigabytes of storage to a LAN. Two years ago, such boxes might have scaled to 0.5TB. Today, a single NAS system may support as much as 30TB.
Data backup was supposed to be a big problem for large NAS devices due to network congestion. But thanks to adoption of the Network Data Management Protocol standard and technologies such as Network Appliance's SnapShot feature, which creates a copy, or "image," of the file system and associated disk block mappings, that's changed. Today, you can run NAS backups over high-bandwidth Gigabit Ethernet networks quite efficiently.
NAS devices have traditionally served up files to end users, while SANs have allowed application servers to access disk storage without a server intermediary and send it in efficient block-data format over Fibre Channel, a dedicated, high-speed serial interconnect. But NAS is now well established for adding capacity to e-mail servers, Web server farms and SQL and Oracle databases, where clusters of NAS devices can increase availability and throughput.
Data centre applications such as online transaction processing still work better on SANs, which offer high scalability and faster performance, especially for large files or where storage traffic is heavy. But even "some block-level applications, like an Oracle or IBM DB2 database, are adopting a file system to replace the block storage technique", says independent storage consultant Jon Toigo. "There is a certain convergence going on, and NAS is well positioned to take advantage of it."
NAS servers are relatively easy and inexpensive to install, and users say they've been highly reliable. "It is great because you can distribute it all over the place, and you can manage it from one location," Toigo says.
The technology is not without its limitations, however. Most servers use a Web management interface, which works fine for a single device. But as the systems reach capacity, administrators must add new NAS systems. The problem: "You've got to surf the [individual] Web pages associated with each NAS box to maintain them. That's a hassle," says Toigo.
Then there's storage virtualisation. A single NAS server allows multiple disks to appear as a single virtual storage volume to end users and application servers. And administrators can add hot-pluggable disk drives to the system and expand the virtual volumes on the fly, without disrupting applications using them. But these volumes typically can't span multiple NAS servers, let alone work with other vendors' NAS devices, and that limits scalability. A few startups have begun offering that capability, but the technology hasn't yet trickled up to the market leaders.
"NAS is a great out-of-the-box solution, but you don't have a lot of options in configuring it," says Mike Carrato, a partner in Accenture's New York office. That's one reason organisations aren't loading anywhere near 30TB on a single NAS device today. But users are looking for new ways to use this relatively inexpensive, high-capacity storage, and vendors are looking for new ways to accommodate them. Ultimately, analysts say, IP SANs will offer a single, virtualised storage pool for both NAS and SAN functions. Until then, convergence between NAS and SAN may be the answer.
NAS/SAN convergence is happening at a rapid rate, according to Simon Elisha, senior systems engineer at Veritas.
"Businesses are not prepared for their NAS solution to contain gigabytes or terabytes of captive" storage," Elisha explains. "Therefore, NAS heads' or gateways' are being placed in front of SAN infrastructure to provide NAS services. Basically, any business implementing a SAN can also provide NAS functionality using the same infrastructure base [and in many cases by repurposing existing hardware]."
Storage array vendor and Seagate subsidiary XIOtech is one company that recently added a new solution to the existing list of products providing gateway that converges network-attached storage with storage-area networks.
The company announced a NAS package that lets administrators tie block-based XIOtech Magnitude storage arrays to NAS file servers so users can access data from their workstations as file-oriented data.
To configure XIOtech's NAS package, a server that uses Novell's or Veritas's NAS software attaches to the network and also to the XIOtech Magnitude storage array. Novell's NetDevice NAS is installed on any industry-standard Intel server; Veritas's ServPoint NAS for Solaris 8 installs on any Intel or SPARC-based Solaris server.
Other SAN/NAS hybrids, like IBM's NAS 300G, place a NAS front end on a Fibre Channel SAN to convert client file requests to block data requests.
However, the NAS market is still fairly new and that, according to Elisha, means that organisations are only starting to learn about the mistakes they made in their choice and implementation of it.
"People have made some major mistakes with NAS, " Elisha says. "A lot of organisations [have] locked in to poor technology, [some have] storage captive in NAS devices, no SAN strategy, no consistent management platform, etc. [For them], NAS is a point solution that has simply added another management headache for IT departments."
Elisha sees wasted resources, inefficiency and lack of scalability as some of the main problems facing these companies.
"The backup and recovery of NAS devices is [still] horrendous," he explains. "It requires dedicated drives [wasted resources] the use of NDMP [inefficiencies] and makes no use of the SAN for data transport. Also, most solutions do not scale well into the enterprise space or have to employ a forklift upgrade' replacement strategy to scale."
What distinguishes a good storage implementation from a bad one is the ability to utilise existing infrastructure to implement NAS technology in a simple and high-performance manner, according to Elisha.
There are several criteria to measure NAS performance, but Elisha lists the use of scalable, freely available hardware, the ability to back-up using the SAN, the ability to use any and a combination of storage vendors for a NAS solution, a highly efficient and highly available file system, and an intelligent combination of SAN and NAS technologies to help realise cost savings and administration flexibility, as the main ones.
"The whole point of NAS is that it is cheep and cheerful," says Ed Dieter, manager of international sales at XIOtech. "It has a place in organisations that don't want to jump to the full complexity of SAN."
Dieter points to NAS's ease of
implementation as one of its main selling points. However, like Toigo and Elisha, he warns about its scaling problems, arguing that they need to be managed separately.
Organisations are only starting to realise the impact of their NAS decisions. While the market is converging rapidly and better management tools are at hand, its enterprise viability has yet to be measured. Cheep and cheerful it may be, but the success of NAS is ultimately going to be measured by its efficiency, availability and scalability - in other words, in terms of its ROI.
For as Elisha puts it: "Storage is not a toaster, it is storage."
NAS by class
Enterprise-class NAS: For enterprise-class network-attached storage, EMC's Clariion and Network Appliance's NetApp filer servers still rule. The devices can scale to nearly 30TB and offer the most advanced management tools - including the ability to work with enterprise network management tools like Computer Associates International's Unicenter TNG and Hewlett-Packard's OpenView. "EMC has the leading storage management software in Control Center. They're very well placed to serve whatever you need to do - if you can afford them," says Mark Roberts, principal of Dataphile Consulting. These vendors also offer enterprise-class support programs and proven reliability.
Departmental filers: Filer servers from vendors such as Quantum and Maxtor offer an easy way to add inexpensive storage in remote offices, departments or small to midsize businesses. They're good for adding a quick 300GB of storage on a departmental LAN but are more unwieldy to manage as the number of NAS servers grows. If you're using NAS devices to consolidate Windows servers, look for systems that use Microsoft's Common Internet File Services (which supports Active Directory) rather than the Unix-based Network File System.
Recently, Procom Technology introduced the NF800, a departmental filer that competes with Quantum and Maxtor. It runs the same journalling file system as Procom's Unix and NT-compatible mid and high end filers, has a SCSI port for direct connect backups; and its fans, power supplies and disks are all hot swappable without taking the box offline or requiring major disassembly. According to Procom, it is also capable of running Procom's disaster recovery software, which sends across the changes of data and requires less bandwidth/pipe compared to other DR products.
The innovators: Startups are the great innovators in NAS technology. For example, LeftHand Networks and Tricord Systems can virtualise and centrally monitor storage across multiple NAS servers, creating highly scalable storage systems that can be distributed for greater fault tolerance. And Tek-Tools is working on XML-based agent technology that will allow management of multiple vendors' NAS boxes from a single management screen.