Overview
Much has changed in the three years since Riedel’s 1997 study of sequential I/O performance [Riedel]. Disk capacities have increased; today’s biggest hard drives are over four times larger than the largest drives available then. Single disk sequential I/O throughput has also improved with 10,000 RPM drives. Processors have increased in speed and number. SMP is now available for the desktop. Memory and system buses have improved. SCSI has also improved over the last two years with Ultra160 SCSI promising a four-fold improvement in adapter to disk bandwidth. With today’s technology, we were able to achieve almost 24 MBps of read throughput on a single disk. Write throughput on a single disk peaked out at 22.5 MBps. This represents a 2.5 to 3 times improvement over the throughput Riedel measured. The disks used for our study were representative of drives commonly available at this time but not necessarily the highest performance disks on the market. The fastest drives now exceed 30 MBps in sequential transfers.
The software landscape has also changed, as Windows 2000 is replacing Windows NT4. Windows 2000 introduced dmio, a new volume manager, to replace ftdisk. Despite the fact that dmio and ftdisk are very different in implementation, our IO performance measurements show only minor performance differences between them. Processor overhead for dmio is somewhat higher so a processor-bound application might see a slightly different picture.
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