The importance of enterprise storage was highlighted some time ago by consultancy Merrill Lynch in its Storage Futures report, which warned that storage demand will double every year for the next few years. Traditionally, most storage has been internal to the server or server-attached. Now however, there is a growth in more sophisticated storage approaches, such as storage area network (San) and network-attached storage (NAS). According to Merrill Lynch, the technologies only account for 8% of the storage market today, although this figure is set to rise.
So what are the differences between San and NAS? More importantly, what are they going to do for the business?
Sans are basically high-speed specialist networks that connect different types of storage devices with data servers on behalf of a large network of users. Unlike NAS, they shift data blocks around and predominantly use a SCSI protocol over Fibre Channel.
Generally speaking, a San is usually clustered near existing computing resources, such as mainframes - but can also extend to remote locations for back-up and archival storage.
Typical uses of Sans include back-up and restore, disc mirroring, data migration, tape resource sharing and archival, and retrieval of data. The technology has a reputation for high performance, although standards issues mean that it is yet to deliver on its full potential in terms of multi-vendor environments.
Conversely, NAS is set up with its own network address as opposed to being attached to the department computer serving applications to a network's workstation users. The general consensus is that by removing storage access and its management from the department server, both application programming and files can be served faster. The other big benefit is that it is much easier to share files and storage areas across multiple clients and operating systems. Typically, the NAS device is attached to a local area network (Lan) and given an IP address.
One of the great strengths of NAS is its versatility. It can be integrated into a San, used as a building block on the way to implementing a San, or simply exist in its own right. This is an interesting point, and one which appears to be getting through to users. One industry expert explains, "The two technologies are more complementary than competitive."
The advent of Direct Access File System (DAFS) should hasten this integration. Stuart Gilks, system engineering director of NAS specialist Network Appliance, says, "DAFS is a file-sharing protocol that runs over the virtual interface which can sit on Fibre Channel, Gigabit Ethernet or Infiniband."
According to Network Appliance, DAFS is a key element in providing integration of San and NAS - thanks to the fact that it can be deployed over existing infrastructures. Gilks says, "Because DAFS can co-exist on both NAS and San we see it as being a very important enabler for our customers."
For a long time regarded as something of a niche product, NAS is becoming increasingly attractive to companies struggling to meet the demands of the e-business revolution. Offering low infrastructure costs and an impressive file sharing capacity, it could be the answer to business storage needs. Gilks explains, "The biggest difference between NAS and San is the location of the file system intelligence." Whereas San focuses on sharing resources, NAS is ideal for the task of sharing files between heterogenous servers.
Network Appliance claims to provide NAS systems that can offer more than 10 terabytes of storage from the box, which is ideal for users that need to get their NAS up and running in a short space of time. It also maintains that the Network Appliance filer products such as the F840 let people access their files, regardless of the operating system.
According to Merrill Lynch, storage is central to the third wave of industry evolution, Internet computing. Moreover, server-attached storage is giving way to San and NAS, which are growing at 67% a year. Major players such as Network Appliance, EMC and Veritas have been identified by Merrill Lynch as being firmly in the sweet spot of the storage market.
The future for NAS certainly seems bright. Businesses today are much more comfortable with the idea of storage networking and, as ever, want the most "bangs per buck". The San, while offering impressive performance, has been held back by the fact that standards are still in their infancy. Moreover, Fibre Channel Sans can be expensive and time-consuming to implement.
Nonetheless, a number of companies are already reaping the benefits of Sans. One of Britain's biggest mortgage lenders, the Halifax Group, recently deployed a San to support its UK operations. According to the financial services giant, it has deployed more than
50 Brocade Silkworm fabric switches in one multi-fabric San. Halifax Group has also deployed several other Brocade-based Sans across the company. The company's technologist, Bob Sibley, says, "This configuration creates a single fabric infrastructure for transparent data replication between systems and sites."
The San has also helped Halifax implement Lan-free back-up, giving the organisation significantly better back-up performance, he says. If it's back-up you are after, then you should seriously consider a San.
Moreover, interoperability, although not completely resolved, is becoming less and less of an issue. Chris Boorman, of software management giant Veritas, says, "Customers are looking for return on investment so we are working with the vendors on the software to ensure that users have interoperability."
The software firm, which claims to be equally at home with both NAS and San architectures, already has a number of offerings that can help users get the most out of their San and NAS by managing their storage networks.
Even if San and NAS technologies are comparatively new, there are valid business cases for implementing them. For example, the benefits of using Sans to free back-up from the Lan are widely acknowledged. NAS, on the other hand, is fast gaining a reputation as a technology that is extremely cost-effective and easy to implement.
Ultimately, spiralling volumes of data over the next few years will force a number of companies to implement one of the technologies, maybe even both. Boorman concludes, "The whole debate about NAS and San is about providing solutions that customers want."
Case Study: Nationwide builds central San pool
Nowhere is the need for storing corporate data more important than in the financial sector. Perhaps it is not surprising that Nationwide claims to be on course for a very important first. To be the first UK organisation to deploy a successful San solution.
Describing itself as the UK's biggest building society, the technology stakes for Nationwide are extremely high. With about eight and a half million customers generating 1.3 million transactions every working day, it is clearly crucial that the company gets its IT infrastructure right. Martin Conway, Nationwide technical consultant, explains, "To make sure that the society keeps its promise to its members, we need high performance and resilience in the technology infrastructure."
Thus, over the past few years the building society has been developing an enterprise storage strategy for mainframes and servers that allows storage to be a centrally managed pool. The Nationwide team looked at the one place where all the computing came together, the data level in the storage systems. Recent developments in San technology, particularly in the capabilities of Fibre Channel networking, have given Nationwide the technology building blocks to develop the strategy a stage further.
Using an access hub from StorageTek at its heart, Nationwide's San has enabled the company to develop Fibre Channel networking to improve performance and link a wide range of hardware and applications. Nationwide ran its first trials at its testing and recovery site and were impressed by its flexibility. The San, with the access hub at the centre, is now connected to products from EMC, Digital, Compaq and Emulex.
The first San project covers an MS SQL 7 server environment at Nationwide's test/development site. This includes running four Fibre Channel loops simultaneously from one NT server for resilience and performance. In the future, Nationwide will implement a San to provide generic Windows NT server disc connectivity in Swindon and develop an NT server back-up to support the sharing of tape devices between multiple NT servers.
Case Study: Airflow Streamline sees advantages of NAS
It is no surprise that the manufacturing division of a company such as Airflow Streamline - which builds cab assemblies for industrial, agricultural and commercial vehicles - relies heavily on its data.
The challenge for Airflow Streamline's IT staff was that the design centre employed a variety of computer-aided design and manufacturing packages that were generating huge volumes of files that were stored on the users' workstations, not on a central storage facility. This meant that when data had to be backed up, support staff had to trudge across the site in all weathers and manually change tapes in drives that were connected to individual machines.
Worse still, office applications used by the company's 150 staff were running on three servers that were also soaking up storage capacity.
It was felt that the answer to these problems was to centralise and automate storage practices as much as possible by consolidating all data storage into one solution. The dilemma for Wayne Sheldon, Airflow Streamline's computer manager, was whether to choose NAS or San technology. Ultimately, the company opted for a NAS NS2000 system from Auspex Systems, citing scalability and cost as major selling points.
Sheldon explains, "It was scalable to a degree, which would long exceed the forecast growth in storage needs, but not at a price that would prevent adding extra discs or cabinets."
He also identified the fact that the NS2000 is capable of handling files from Windows NT and the wide variety of Unix formats that Airflow Streamline's customers use.
Once up and running, administration functions that had previously been running on a standalone server were moved across to the NS2000, effectively freeing up the server to run the company's e-mail services.
The system can also recover files that have been deleted or simply misplaced by end-users. In this way, administrators can take periodical snapshots of the file systems on the server. If a file is accidentally erased or lost due to data corruption, the administrator can select the file as last recorded in the snapshot and recover it from the NS2000 or restore from tape.
This was first published in November 2001