Apple's Xserve RAID offers storage flexibility, speed

In my previous column, I profiled Apple Computer Inc.'s Xserve G5 server (see story). The second piece of Apple's high-demand server lineup is the Xserve RAID, a high-performance network storage device.

While the Xserve and Mac OS X Server are designed to work together as a multifunctional tool -- providing virtually every common network resource and service -- the Xserve RAID is designed to do just one thing: securely store large amounts of data and provide extremely fast access to that data. It's designed to work with any server platform (Mac OS X Server, Windows or Linux) to provide easy-to-manage, high-speed network storage.

Like the Xserve G5, The Xserve RAID uses Apple's hot-swappable hard-drive modules. Each module can hold a hard drive offering up to 250GB of storage, and each has a dedicated data channel and an 8MB onboard cache. Like the Xserve G5, these modules can be removed and replaced without interrupting the Xserve RAID functionality. Unlike the Xserve G5, which has three drive modules, the Xserve RAID has 14, allowing for 3.5TB of data storage.

Although tremendous storage capacity is important, fault tolerance and the ability to stripe the hard drives into an array is, for most administrators, a more critical need in a network storage device. The Xserve RAID supports all major RAID types, including the traditional disk mirroring (RAID 1) for fault tolerance, striping without parity for maximum speed improvements (RAID 0) and striping with parity for both speed and fault-tolerance advantages. (RAID 3 and 5). All of these are supported at a hardware level, removing the processor overhead associated with software-based RAID.

Including hardware RAID capabilities also allows administrators to create hybrid arrays (such as RAID 1-0 and RAID 10, 30 and 50), in which multiple hardware-based arrays can be combined to create a software-based array. For example, in RAID 50, multiple RAID 0 striped arrays are created, and then all the arrays are treated as individual drives and combined into a further striped array using software-based RAID.

The Xserve RAID comes with a series of intuitive tools, similar to the Mac OS X Server monitoring tools, which make creating hardware-based arrays incredibly simple. The created arrays can then be formatted or further combined into software-based arrays using Apple's Disk Utility.

Management of an Xserve RAID is accomplished using the device's Ethernet port, which provides an access channel independent of the Fibre Channel network ports used for data storage access. Locating an Xserve RAID with monitor and management tools is made simple with Apple's rendezvous technology.

The Xserve RAID also includes a serial port for connection to a uninterruptible power supply to maintain safe functionality in case of a power failure or power fluctuation. To further provide for data integrity during power problems, Apple provides two optional cache backup battery modules, which can maintain power to the onboard cache of each drive module for up to 72 hours.

The Xserve RAID isn't something that everyone needs. Many Macintosh administrators will never need to provide the amount of network storage and performance that the Xserve RAID affords. However, quite a few will, and the Xserve RAID's design, which is based around both performance and fault tolerance, has all the hallmarks of being a great product for them.

Ryan Faas has been an IT professional and technology writer specializing in Macintosh for nearly 10 years and currently manages the Mac OS X Server and Macintosh workstations at a community college in Upstate New York. He is also co-author of Troubleshooting, Maintaining, and Repairing Macs (McGraw-Hill Osborne Media, 2000).
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Copyright © 2004 IDG Communications, Inc.

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