A channel professional quickly learns that selling server hardware to management is easier when the hardware has a clear purpose. Even if management understands the need for RAID, the system has to be deployed simply, reliably and on budget. This is where Apple Xserve RAID comes in. This product offers industrial hardware strength with management software that's advanced enough to make RAID deployment simple. Eliminating administration headaches means TCO can drop dramatically on the backend.
Despite prevailing myths floating around the channel, Apple's Xserve RAID works in all-Apple or heterogeneous environments. It can fit into existing storage networks or provide a basis for new storage installations.
The SFP-based Fibre Channel interface supports point-to-point, loop and fabric topologies to integrate the 3U Xserve RAID into Fibre Channel storage infrastructures. In addition, a platform-
independent design and Java-based administrative tools make monitoring simple from an Internet-connected computer. Xserve RAID teams with Xserve, Apple's 1U server, to provide an alternative to traditional network-attached storage (NAS) devices.
Redundant, hot-swappable components and a passive midplane data path are used to protect data from single points of failure, while independent controllers and 14 drive channels provide high-speed throughput to deliver data to the host system. The midplane is the central connector between the drives, RAID controllers, power supplies and cooling modules. Unlike other RAID hardware setups, Xserve RAID does not use it for any data transfer.
Xserve RAID supports RAID levels 0, 1, 3, 5 and 0+1 using the RAID processor, as well as hybrid RAID levels 10, 30 and 50 by combining its hardware RAID capabilities with host-based software RAID.p>
Leading storage infrastructure vendors have certified Xserve RAID to integrate with existing Fibre Channel hardware and data management solutions. These vendors include:
- QLogic
- Brocade
- McDATA
- Emulex
- Cisco
- Veritas
- ATTO Technology
- LSI Logic
RAID Admin, an Xserve administration program, integrates with hardware to continuously monitor system activity and status. Environmental management coprocessors in the RAID controllers connect to the host system via Ethernet, providing dedicated, out-of-band system management capabilities. This improves system performance and reliability, because there is no contention for bandwidth with the RAID processors or the Fibre Channel interface.
To share a single RAID set across multiple servers, RAID Admin allows the channel professional to divide RAID into smaller segments or "slices." Each slice becomes a separate logical unit number (LUN), so the host system can manage it as a discrete volume. Instead of creating many small arrays for individual servers, this "pooling and distributing" technique enables you to leverage the storage efficiencies of a large consolidated array. RAID Admin can slice up to eight LUNs per RAID controller or up to 16 LUNs per Xserve RAID system.
When you connect an Xserve RAID to more than one host system on a Fibre Channel network, you can "map" each LUN on the RAID system to a single host and "mask" it from any other host. By masking arrays and slices, you avoid the possibility that more than one host will write data to an array, greatly reducing the risk of array corruption or data loss.
A single Xserve RAID power supply can sustain the system in the event of a power outage or electrical surge. Each RAID controller has its own DB-9 serial port, which allows the Xserve RAID to connect to and monitor up to two UPS sources. When the system detects that input power has been switched to a UPS source, it changes the cache mode from high-performance write back to a safer write-through cache -- protecting data transactions should the UPS fail. If the UPS system is capable of reporting a low power level, Xserve RAID can alert the client of the condition, permitting a manual shutdown before the power runs out.
About the author: Larry Loeb has been online since the world revolved around {!decvax}. He's been in many of last century's dead tree magazines about computers, having been a consulting editor to the late, lamented BYTE magazine, among other things. You can reach him at larryloeb@larryloeb.com.
