IBM helps capacity match users

Any planning document coming out of IT these days is bound to make heavy use of the term “consolidate.” Applied to storage, consolidation means maximizing the capacity of your most capable arrays, servers, and networked storage devices. If you’re relying on 36GB and 18GB drives now, you can expand your capacity by a factor of four or eight without consuming more rack space or raising power and cooling costs.

One such solution is IBM Corp.’s 146GB Ultrastar 146Z10, a low-profile, 3.5-inch device with an Ultra320 SCSI or 2Gb Fibre Channel interface. Its rotational speed of 10,000 rpm, 4.7ms seek time, and 8MB cache lend a boost to the 146Z10 compared to IBM’s previous 10K models. Seagate Technology LLC and Maxtor Corp. have answered with similar drives, the 10.6 Cheetah and the Atlas 10K IV, respectively. Hitachi Ltd. announced a 147GB drive as part of its EJ series of 10K devices.

Physics limits the minimum size of a particle that can remember whether it’s a 1 or a 0, which places a ceiling on hard drive data density. IBM sprays each platter of the 146Z10 with an AFC (antiferromagnetically-coupled) material. The AFC coating breaks through the old density cap, thought to be between 20GB and 40GB per square inch. IBM expects to achieve 100GB per square inch in 2003.

That incredible density makes a hard drive a precision instrument, and turns an array into a torture chamber. Vibration from adjacent drives knocks read/write heads out of alignment and drastically reduces their throughput. IBM uses motion sensors in the 146Z10 to compensate for vibration, so the heads have a better shot at transferring data on the first pass. Seagate elected to use a passive damping system to solve the same problem for its latest enterprise drives.

We tested a pair of 146Z10 drives using an Intel rack server with dual 2.8GHz Xeon processors, running Windows 2000 Server. That system’s on-board Ultra320 SCSI controller is aided by an Intel RAID controller.

The 146Z10 is the first drive of its class we’ve seen in the lab. We had to compare it to something, so we chose the fastest unit in our testbed: the Seagate ST318451LW, an 18GB, 15,000 rpm drive. This wasn’t a head-to-head test; our Seagate drive is at least a generation behind IBM’s technology. Still, we were curious how the 146Z10 would stack up against the performance champ.

The IBM and Seagate enterprise drives are similar in power usage and heat dissipation. The 146Z10 is much quieter than the older 18GB Seagate. IBM’s drive is so quiet, we had to trust our test software to tell us the drive was running. When idling, the drive emits a strange “bark” at intervals, a sound we attributed to the loading and unloading of the drive’s heads. That’s a data safety and power conservation feature that you can tune with software.

The 146Z10’s performance was in line with our expectations. Asynchronous writes, which assemble data in the drive’s onboard cache before writing, were about 35 per cent faster on the 146Z10.

When we disabled the drives’ buffers to test synchronous writes, the Cheetah was faster than the 146Z10 by about 50 per cent. That’s what we expected given the 146Z10’s larger buffer and Seagate’s 15,000 rpm rotation.

The Ultrastar 146Z10’s performance in our simple tests was more than adequate, and the drive’s asynchronous performance is outstanding. Its speed, coupled with the drive’s low noise and level power requirements, makes IBM’s flagship enterprise drive a good choice.

Drives in this class are perfectly suited to satisfy IT’s primary objectives: reduce operating costs and match capacity to users’ needs. IBM’s engineers did a fine job marrying larger cache with vibration-compensation technology.