Dafs to take NAS to the next level

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Dafs to take NAS to the next level

Network-attached storage (NAS) was the big growth area of 2000 and now a new development looks set to improve performance, writes Nicholas Enticknap.

Network Appliance, the NAS market leader, doubled in size last year to become a billion-dollar company. Its success has attracted industry giants such as Compaq, Dell, Hewlett-Packard, IBM and Sun Microsystems to the market.

Although the scramble for market share has become a real dogfight, the technology has stayed the same: a mechanism for sharing files over a local network using the NFS (Networked File System) and Cifs (Common Internet File System) protocols.

This is going to change when a new spin on the NAS theme is launched, the Direct Access File System (Dafs) protocol. Version 1.0 of Dafs is promised for July and the first products are expected to arrive before end of the year.

The main benefit for the user is performance. Dafs is designed to allow bulk data transfers without operating system intervention and with minimum use of processor cycles.

It does this by using the direct memory-to-memory access facilities offered by new interconnect technologies such as VI (Virtual Interface) and Infiniband, which are being developed to allow server clustering with high performance. As a result, Dafs spends more time transferring data and less time working out how to make the transfer.

"Dafs, in combination with next generation servers built around the Infiniband architecture, should enable a much higher level of efficiency than today's datacentres can achieve," said Mitch Schults, Intel's server business development director.

Mark Simmons, an analyst with Bloor research, said, "It is faster than the current method of doing things. It is going to be a way forward. Access to information over different architectures is becoming cumbersome, so it is needed."

The development of Dafs has been both quick and quiet. It is less than a year since the intention to develop it was first announced in a joint statement by Intel, Network Appliance and Seagate

Technology.

Shortly after the announcement the Dafs Collaborative was formed to develop the protocol. The consortium, which now boasts over 60 member companies, has steadily got on with its job and by last month had completed 75% of the Dafs specification.

Development has been quiet because it has not been accompanied by any of the promotional zeal that has surrounded other storage standards such as Fibre Channel and iSCSI. Although the specification is only a couple of months away, Dafs is still virtually unknown.

Only two companies, Intel and Network Appliance, have been actively promoting Dafs. For Network Appliance it has been a case of ensuring that NAS evolves in line with other industry developments while fending off competing storage offerings such as iSCSI storage area networks.

For Intel, Dafs has been included in its promotion of VI. Dafs will be the first VI application.

This absence of promotion may delay acceptance of Dafs. The list of consortium members includes major storage players such as Compaq, Hewlett-Packard, IBM, Oracle and Veritas. However, other potential players, such as EMC, Hitachi and Sun, are conspicuous by their absence.

Some of those onboard are merely there to keep an eye on developments, rather than as committed adherents. Clod Barrera, IBM's storage division technology director, said, "IBM's position is that Dafs is a very interesting technology We are interested in finding places in the market that can use it but we are not convinced it will completely conquer the landscape."

The Dafs Collaborative has not yet secured the commitment of any of the established standards bodies, nor has it brought the analyst community onside to help beat the drum.

On the plus side, systems offering Dafs support should be easy to implement. Dafs is a high-level protocol that defines capabilities rather than the method of implementation. Dafs systems will work with present TCP/IP networks provided only that Dafs-compliant network interface cards are added to the participating servers.

It is also a new capability rather than a replacement for an existing one. VI is optimised for communications over high-speed, low-latency networks, such as exist in data centres. NFS and Cifs were designed for use in larger networks.


How does Dafs improve on NAS?
Dafs is designed to allow bulk data transfers without operating system intervention and with minimum use of processor cycles.

It does this by using the direct memory-to-memory access facilities offered by new interconnect technologies such as VI (Virtual Interface) and Infiniband, which are being developed to allow server clustering with high performance. As a result, Dafs spends more time transferring data and less time working out how to make the transfer.

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This was first published in May 2001

 

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