Storage: when NAS met SAN

Two enterprise storage technologies that were fighting each other for customers have now taken off the gloves and committed to...

Two enterprise storage technologies that were fighting each other for customers have now taken off the gloves and committed to working together

For some time now, Network Attached Storage (NAS) and Storage Area Networks (SAN) have been seen as alternative solutions to the problem of storing enterprise-sized amounts of data.

SAN has been seen as a solution to issues such as bandwidth problems and storage accessibility by providing a separate network optimised for storage. NAS, on the other hand, works within the existing LAN infrastructure in order to position storage where it is needed.

Those on the NAS side have claimed that a true SAN is a long way from full implementation and expensive to implement, while SAN supporters have said that NAS is not flexible or accessible enough and takes up large amounts of precious network bandwidth.

Now it seems that the two sides have decided to put their differences aside and, in a spirit of co-operation, have finally admitted that NAS and SAN are not competing technologies, but complimentary ones. A recent report from Bloor Research claims that the two are not mutually exclusive, and "either or both can be used to solve the specific issues than an organisation may face".

Companies from both sides of the storage debate are now saying that NAS technology on the network could be relatively easily integrated into a SAN environment, strengthening the storage capabilities of an enterprise. Bringing the two technologies together could solve problems that NAS or SAN would not be able to fix by themselves.

David Hill, analyst for Aberdeen Group, says: "Customers are clamouring for storage system investments that will meet today's needs but are also flexible enough to accommodate tomorrow's storage capacity. Adding SAN capabilities to NAS does this by creating a highly scalable system that can grow with the customers increasing storage requirements. NAS and SAN technologies each have their own advantages, making them an excellent complement to one another by increasing overall storage capacity and speed at an affordable price."

Many companies have turned to Network Attached Storage as a cheaper and more easily implemented way to backup and share stored data. Once NAS is fully installed on a network it would be difficult to justify a complete switch to SAN, even if the technology and infrastructure would suit the business better. The costs of a changeover would be huge, the logistics would be a nightmare for larger companies, and it could well leave the companies' data unprotected during the changeover. An intermediate step allows for a much smoother changeover that does not render most of the storage technology currently in use obsolete. It will also pave the way for the integration of a full SAN solution, whenever that time arrives.

Now, vendors are finally coming together to bring backup systems using both SAN and NAS to customers. Six such companies have recently collaborated to introduce an integrated NAS-SAN offering in what they say is a response to the industry's need. Vixel, Legato Systems, Network Appliance, Quantum, ATL, Spectra Logic and Veritas are claiming to be the first vendors to be able to provide a complete NAS-SAN solution for data protection.

Arun Taneja, vice president, marketing for Vixel, says: "At the end of the day, customers typically care most about resolving their IT issues and enhancing their competitiveness, and will deploy the appropriate technology to achieve that. Both SAN and NAS have demonstrated their usefulness in different areas. Those spearheading this solution have demonstrated how the integration of the best from both SAN and NAS can ideally address a real problem for the storage-centric IT customer."

We can look at an example of a heterogeneous network environment, such as a LAN supporting NT and Unix servers. Data could be shared with both operating systems via multi-protocol file servers and backed-up on a tape drive connected to a dedicated backup server. This would help fulfil basic storage requirements but could cause problems for the network when implemented. LAN-based backup will require that one or more storage servers be placed on the network. The regular backup procedure will be carried out via the LAN using IP protocols. Unfortunately, this then competes with end users, who are accessing data through the network, for data bandwidth. The sheer volume of data that a backup transfer can generate may create severe bandwidth resource problems, even in the most sophisticated switched network environments.

A possible solution to this problem is to schedule backups for times when the network is not in high use, such as overnight, but even then the sheer volume of data needing to be transferred may mean there is not enough time to do so. Also, there are an increasing number of companies operating on a 24-hour basis, and many companies, such as ISPs, cannot afford any risk of downtime whatsoever.

Another possible alternative is to attach tape drives directly to the file servers via SCSI, therefore taking the backup off the network. The problem with this option is that it will require a tape drive for each and every file server, increasing the cost of backup substantially as well as the complexity of managing the drives and backup procedure. This also means that because the stored data is spread around several different tape drives across the network, it cannot easily be retrieved or shared between the file servers.

In this situation, it could be of great advantage to implement the hybrid NAS-SAN solution. A fibre channel SAN could be relatively easily integrated with the storage already on the network in order to remove backup traffic from the LAN. This would free up valuable bandwidth resources and offer greater accessibility for retrieving lost data.

Instead of attaching tape drives to every file server or to a backup server on the network, a Fibre Channel switch could be introduced. File servers storing data could then be attached to the switch directly via fibre, the switch in turn would then attach directly to one or more tape backup drives. This ensures that the data is stored in a single place making recovery much easier. Also, because the drives are not placed in numerous places around the network, manageability of the backup and recovery procedures is far simpler and much more efficient.

For larger networks, numerous file servers can be integrated into the same SAN with mid-range tape drive and larger tape libraries sharing the responsibility of data access and archiving. Fibre Channel can also work over distances of up to 10km and so can provide disaster recovery options for those wishing to undertake that.

The biggest advantage of all though is that because all the tape drives have been removed from the network and connected to the file servers via a Fibre Channel switch, the Ethernet network is left uninterrupted and the bandwidth is freed up to increase speeds for end users.

This option, although not a true SAN solution, does offer many of the benefits that SAN professes to bring. In fact, it is widely recognised in the storage community that the day of a fully functional, truly intelligent SAN is still some way off.

Some competing vendors continue to promote proprietary solutions instead of championing the cause of a single common standard for SAN technology. This situation is slowly changing however. Many of the vendors are coming together to provide multi-platform solutions, unfortunately, there are still several different solutions out there from various vendors. Until the industry pulls together to create offerings that comply with a universal standard, the take-up of SAN technology by customers will continue to ramp slowly.

NAS too is still in the early adopter stage, and has the price premium to go with it, but this should change in the near future as the technology becomes more prevalent. Companies that had previously held off buying NAS technology, waiting for a truly intelligent and affordable SAN solution to appear in the market can now reconsider their options.

There are also those enterprises that have gone ahead and installed NAS only to find that the business has developed to a point where SAN would be a more preferable technology. Previously, adopting NAS could have blocked off an easy and affordable route to SAN. Now, whether by accident or design, vendors have once again opened up the road to SAN for those who have adopted, or are thinking of adopting NAS technology.

It is quite possible that if it were not for customer demand, the two technologies would have remained as competitive options. This may well have stifled both technologies progress into the market, a situation all vendors in storage desperately want to avoid, considering how unprofitable the lower end of the market has become.

Companies in both the NAS and SAN markets will no doubt benefit from a blending of the two technologies, but hopefully the real winner will be the customers, who should now be able to pick what enterprise storage they want, when they want, and how they want it. With the great amount of interest being taken by the major vendors in these technologies, competitive pricing is also going to offer better deals for potential buyers. As time goes on, more players will enter the market and prices should fall even further.

NAS and SAN may initially seem like unusual bed partners, but the technologies are not too far away from each other and are getting closer every day. It's possible that this sort of hybrid offerings will become standard in network enterprises, rather than just part of a roadmap to SAN. But at least now, whatever suits your business best, the option is at least there.

Paul Grant

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