Serving Up Storage

Faster SCSI and Fibre Channel SANs set the stage for servers that run and run.

Scott Mace

Disk I/O subsystems, not CPUs, are the bottlenecks in today's servers. However, that will change in 1998.

The changes start with the venerable SCSI, which is suddenly doubling in speed and length, going from a 40-MBps burst rate to 80-MBps with PCI Ultra2 SCSI. At the same time, Adaptec has released technology to increase the length of SCSI cables from 3 meters to 12 meters.

The speed improvement will help servers keep up with processor improvement, while preserving investments in previous SCSI hardware. Ultra2's 25-meter distance wil l help drive disk storage out of the confines of the server cabinet itself and into rack-mounted external RAID and more exotic subsystems. Mixing and matching external disk to server will become commonplace. And next year, Adaptec will be sampling Ultra3 technology, doubling SCSI's burst rate again to 160 MBps.

But SCSI is just the beginning. Fibre Channel, an ANSI-standard network that can multiplex both SCSI and IP traffic, extends 30 meters over copper wires or as far as 10 kilometers on fiber-optic cables. It is capable of speeds in excess of 100 MBps in both directions. In 1998, expect to see host adapter offerings from HP, Compaq, and others. Fibre Channel networks will come to resemble Gigabit Ethernet networks, employing hubs and switches as the core of server farms.

Overlaying both SCSI and Fibre Channel are emerging Storage Area Networks (SANs), such as those from Computer Network Technology and Tricord. SANs not only separate storage nodes from server nodes on networks, they also let di fferent servers share a common pool of data. SANs let users expand disk capacity without having to bring down application servers.

Mere speed and capacity are one thing, but affordable disaster recovery and scalability are the holy grails of the data center. Unix systems have offered clustering technology, with automatic failover to backup servers, for years. Disk mirroring has been a feature of Novell's SFT III for almost as long. This year, Microsoft's Server Cluster option brings to Windows NT 4.0 similar reliability features. After NT5.0 ships, Microsoft will expand Server Cluster to support more than two nodes, and NT will gain the scalability of those nodes working together to share the load of applications, such as database servers, which are written to take advantage of Cluster Server.

Not to be outdone, the next release of Novell's NetWare, known as Moab, will be able to support 16-server clusters when its Orion option, formerly known as Wolf Mountain, ships. Novell is promising Orion for the second half of 1998.

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Where to Find

Adaptec

Milpitas, CA
Phone:    408-945-8600
Internet: 
http://www.adaptec.com



Computer Network Technology

Minneapolis, MN
Phone:    800-268-0090
Internet: 
http://www.cnt.com




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Servers Link Up with Storage Area Networks

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High-speed storage subnetworks can employ SCSI, Fibre Channel, and wide-area media such as ATM or DS3 connections.

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Adaptec and Computer Network Technology in 1998

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AT A GLANCE: SCSI improvements and Fibre Channel growth will let servers separate into compute and storage nodes, setting the stage for fault-tolerant, scalable cluster solutions.

WHO SUPPORTS IT: Adaptec, Intel, Computer Network Technology, Tricord, Compaq, Hewlett-Packard, Tandem, Microsoft, Novell, Sun, SCO, Data General, Fibre Channel Association, Vinca.