The NAS/SAN convergence

Roberto Sigona, IT director at Autodesk Inc. in San Rafael, Calif., was peeved about how long it took to back up files on his Windows 2000 network. He had several 500G-byte drives containing file-level data. “It was difficult to seamlessly replicate or back up the NT file system to a different location – physically, it would cause us weeks of downtime,” he says.

What Sigona wanted was the ability to back up the Windows network-attached storage (NAS) servers with the same efficiency and reliability as backing up his storage-area network (SAN).

Not long ago, Sigona’s wish would have gone unfulfilled. NAS was NAS and SAN was SAN, and that was that.

But using EMC Corp.’s Celerra NAS/SAN gateway and Celerra HighRoad software, Sigona got what he wanted. With the gateway attached to Autodesk’s Symmetrix arrays, the HighRoad software transports the files over IP but backs up the file-level NAS data across the high-speed SAN. “I get the best of both worlds,” he says.

In fact, Sigona says, NAS data backs up 50 to 60 times faster now that it’s going over the SAN.

And management is much easier, too. “The rest of our storage is centralized on our SAN, so we can use one console to manage NAS, SAN, direct-attached [storage], as well as the backup and replication of data,” he says.

Sigona is not alone among enterprise users who want to converge NAS and SAN environments. Many are clamoring for products that let them use the same applications to manage their NAS appliances, SANs and direct-attached storage, and forgo decisions on how to manage block-level SAN, file-level NAS and DAS data.

And EMC is not alone among vendors responding to these product demands. A host of traditional storage vendors and start-ups are offering or developing products that blend Fibre Channel SANs with NAS and DAS arrays. These products take two shapes – as NAS/SAN gateways that let administrators attach SAN and DAS arrays to a NAS server, or as special-built hybrid boxes that attach existing storage devices for transport across IP networks.

Analysts expect nearly every storage vendor to offer convergence products.

“We are going to see storage vendors overall offering a combined approach that unifies NAS qualities of being able to understand files and the ability to handle block [transfers of data],” says Jamie Gruener, an analyst with the Yankee Group. “That will happen in the next six to 12 months.”

Already, EMC, IBM Corp., Hitachi Data Systems Corp., LSI Logic Corp. and MTI Technology Corp. have retrofit Fibre Channel arrays and NAS appliances into NAS/SAN gateways. NAS vendors Network Appliance Inc. and Xiotech Corp., a Seagate Technology LLC company, promise NAS appliances that will handle block-level data. And start-ups 3ParData Inc., Cereva Networks Inc., YottaYotta Inc. and Zambeel Inc. are making purpose-built NAS/SAN convergence boxes that show promise, says Steve Duplessie, an analyst with Enterprise Storage Group Inc. The start-ups haven’t disclosed product details, but all say their wares will replace or connect to existing SAN, NAS or DAS devices.

With these NAS/SAN devices, SAN-based arrays or DAS servers attach to a diskless NAS head. Software residing on the NAS head then distributes SAN or NAS data over the appropriate network, depending on the size of the data and the best path.

At Autodesk, the EMC Celerra HighRoad software examines requests for data from Windows NT clients and returns the data over the SAN or IP network, whichever it determines would be faster. If the data consists of small files, HighRoad will return it over IP; if the data is characteristic of online transaction processing or other block type, the software will route it over the SAN.

NAS vendor Auspex Systems Inc. and IBM are adopting what Gruener says is perhaps the nirvana of storage. They have promised to attach any vendor’s storage array to their NAS/SAN gateways. They’ll accomplish this through testing, certifying that different storage arrays work with their NAS servers.

Such interoperability won’t be widespread, Gruener says. Rather, Fibre Channel arrays likely will be accessed by a NAS-like file system. “You will see a new architecture that will be a storage array that has a file system as well as a RAID controller,” he says.

Analysts point to two start-ups developing such products. Broadband Storage, still in stealth mode, is expected to place a distributed file system and virtualized management interface over clusters of NAS appliances and SAN arrays, Duplessie says.

LeftHand Networks Inc., and its Network Unified Storage product, lets IT managers decide between file- and block-level data over IP. A future module will handle the data types concurrently.

NAS/SAN convergence “takes application awareness to a whole new level because you are now able to select a storage environment that will turn on for some applications and turn off for others, depending on what you are doing,” Gruener says.

For Autodesk’s Sigona, the ability to use the same storage applications for file- and block-level data made sense. “We wanted to centralize the storage for all our applications whether they were [SAN] or NT-based,” he says.

Rich Brenton, senior technical architect for electric wholesaler PJM in Norristown, Pa., also sees the benefits. He centralized storage administration by consolidating about 18 file-level DAS servers onto an IBM Shark SAN array and placing an IBM TotalStorage NAS 300G between the company’s IP network and the Shark. The NAS 300G routes file-level data over the IP network, and routes block-level data through the SAN fabric. He can now back up his system data from the same spot. “As our data center grew, [maintaining] the [DAS] became a nightmare – [my] support guys were running around swapping RAID drives all the time,” he says.

As advantageous as NAS/SAN convergence can be, it has drawbacks. EMC, Hitachi and LSI Logic NAS/SAN gateways only let arrays from the same vendor be joined to the NAS head, for example. And while vendors have consolidated some applications and management under one interface, they haven’t gone far enough, some sources say. IT managers still can’t share data on the SAN between devices or look at file-level data on the SAN without going through the server, IBM representatives say. Although they want to use one software product for files and another for blocks, they have to use NAS applications for some and SAN for others.

What’s more, moving storage out of the isolated data center and across IP networks puts it at risk of intrusions that before were not possible. Many industry watchers advocate the use of IP Security (IPSec) and Secure Sockets Layer to secure transport of storage data over the IP network . And Cisco Systems Inc., EMC and several other vendors have recently proposed the FCsec specification, a Fibre Channel variant of IPSec, to the Internet Engineering Task Force.

“Some vendors are looking at ways to safeguard their storage networks by better architecture. Others are looking at ways to enforce security in a policy-based approach by reinforcing around the edge of the network,” Gruener says. “The security issues of combining block- and file-level data are challenging because you still need to uniformly enforce security policies against block and file formats.”

While technologies such as logical unit number masking and zoning – methods that partition the data and control access in SANs – work for block-level data, another approach is needed for file-level data, whose access is enforced by the operating system, Gruener says.

The cost of NAS/SAN gateways also varies widely, depending on the amount of storage attached to the NAS head and the cost of the NAS head itself. In many cases, enterprise users already will have the storage they want to consolidate – they will only need to buy the NAS head and software necessary to make it work.

For PJM, making NAS/SAN convergence possible meant buying into the US$30,000 starting price for IBM TotalStorage NAS 300G, Brenton says. “That’s pretty much the reason we went to the 300G,” he says. “We wanted to leverage our existing storage.”

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