To most companies in Canada, the use of storage is often limited to an enterprise mainframe attached to a redundant array of independent disks (RAID).
Unfortunately, with the increase of Internet usage, distributed networks and computing in general, the limitations of direct attached storage via SCSI are becoming more acute.
According to experts, SCSI presents problems of both distance and sharing. The distance between the storage and servers is limited to about 20 feet, while the SCSI bus protocols limit the number of devices you can effectively use.
“Since SCSI is directly attached to one machine, you are limited to using that one machine as the file server and data mover,” said Michael Fishman, a technologist at EMC Corp. in Hopkington, Mass.
EMC’s answer to the problem with direct attached storage has been storage area networks (SANs), which move storage systems to dedicated high-speed networks controlled by Fibre Channel switches.
Fishman said SANs have the advantage of using high-speed fibre-optics which can span two kilometres without repeaters. SANs also allow the use of hubs and switches, which allow you to connect multiple devices to your storage network, he said.
Unfortunately, SANs are often complex and expensive. Large-scale deployments can often take days or weeks, due to the amount of new infrastructure that is needed.
However, NAS systems – the opposite of SANs – offer no such obstacles. Commonly referred to as a “plug-and-play” technology, NAS devices can be set up in minutes because they attach to the local area network like any other network node.
The technology is also relatively cheap as it requires no modification to a company’s network.
“The key differentiator (of NAS) is that storage is actually attached via Ethernet or the IP network,” said Fishman, who also acts as area chairman for the NAS workgroup of the Storage Networking Industry Association in Mountain View, Calif.
“Because of its attachment to the IP network, employees with proper permissions can access storage via the Internet or through LANs or wide area networks,” he added.
And unlike SANs, NAS systems don’t require any unique host bus adapters (HBAs), Fishman added.
Because of the Internet-centric qualities of the NAS topology, many companies are now jumping into the storage market.
In the past, Sunnyvale, Calif.’s Network Appliance has been the biggest success in the NAS market, while its main storage competitor EMC has developed a larger enterprise market for SANs.
However, with its purchase of CrosStor – a company that sold NAS software – last November, EMC has been pushing to make inroads into the NAS market. It has also been working on hybrid SAN/NAS devices.
But while EMC and NetApp have gained market share, other major vendors have jumped into the storage market in an attempt to complement their server lines. They include IBM, Dell, Hewlett-Packard, Compaq and Sun Microsystems.
Cahners IN-Stat Group, an industry research company in Scottsdale, Ariz., expects the NAS market to reach over US$10 billion in end-use sales by 2004.
According to Alan Freedman, an analyst with IDC Canada in Toronto, much of the reason why NAS systems are becoming more prevalent is because companies are looking for better back-up and disaster data recovery.
That’s exactly the reason why Brian Tao chose to deploy a NAS system in 1997.
Tao, a manager of server operations with AT&T Canada’s Internet and e-Business Solutions division, said his main concern three years ago was “just trying to make sure (our) customers’ e-mail wasn’t lost.”
At the time, Tao worked for Netcom Canada, a small Web services company. In 1999, Netcom merged with AT&T Canada, ACC TelEnterprises and MetroNet Communications to become one company.
Now, Tao’s division serves about 165,000 Internet subscribers. The storage system he has put in place also serves 500 desktop workstations in the AT&T Canada enterprise, he said.
Currently, Tao has 20 of NetApp’s F740 Filers in production in AT&T’s data centre in downtown Toronto. About 75 to 80 Sun servers attach to the Filers. Two more F740s and a cluster pair of F840 Filers are in pre-production testing, Tao said. The F840s are destined to be deployed at AT&T’s new disaster recovery centre in Vancouver.
Before purchasing NetApp’s Filers, Tao said Netcom had already been using a NAS topology.
Since the company is a Unix shop, almost all of their services were hosted on Sun Solaris boxes or free BSD.
“So we would have Fibre Channel drives or SCSI drives attached to a general purpose Sun box, and (they) would act as Network File System (NFS) servers,” Tao described. “The problem we had with that was, when it worked it worked fine. But when something came up – the OS crashed, or if you had a failed drive, or if a power supply died or a fan stopped spinning – we found the work and time needed to get the machine back up was just too great. And it was (happening) a little too frequently as well.”
Three years later, Tao said AT&T is storing all of its applications except one on its NetAPP Filers.
The network’s Usenet news application is kept on raw disk because it is cheaper to do, “and we don’t have a strong need for reliability and maintainability in that department,” Tao explained. “Everything else – Oracle databases, Apache Web server content, customers’ mail, Microsoft Exchange enterprise mail system, Remedy trouble ticketing system, Network Inventory system, HP OpenView – you name it, they’re all stored somewhere in one of those 20 NetApps.”
Fishman would be a little surprised at AT&T’s application storage, as he has found most companies prefer to store heavy database applications such as Oracle and Microsoft Exchange on SANs, which can move large blocks of data more efficiently.
Fishman said NAS systems are becoming more popular in publishing, Web development and design departments.
But Tao rejected Fishman’s concerns about the ability of NAS systems to handle scalable database environments.
“I don’t see the scalability (difference) between SAN and NAS,” Tao said. “On the SAN side, you would add more drives and more Fibre Channel adapters. On the NAS side, you might have to add more Ethernet parts or Filers.”
Tao said AT&T prefers NAS systems because of the company’s familiarity with the protocols it uses, such as Ethernet and TCP/IP. His only advice to companies thinking of deploying NAS systems is to remember that some applications were not written with NAS in mind.
“The biggest thing you need to look out for are applications that assume you have local drives, that there is no network involved, or that they want to have raw file system access,” he said. “If you have an application like Oracle Parallel Server for instance, which can read and write directly to disk blocks, obviously that’s not going to work over NAS. There’s that layer of abstraction in between where you can’t get right down to the physical blocks and sectors and tracks and cylinders on a disk.”
IDC’s Freedman also noted it is important for enterprises to ensure the LAN’s OS is compatible with a storage device. Most storage companies say they are OS-agnostic, but Freedman said that’s not always the way it works out.
“For example, it’s easier to integrate Sun storage into a network if you are using Solaris,” he said.
For more information about NAS, visit SNIA at www.snia.org.