The goal of the "Beowulf Data Server" project is to develop a
The prototype system is being constructed from dual processor Intel P6 motherboards. While the processing power of the P6 might seem to be overkill for a machine that's designed for I/O, there are several factors that led us to this selection:
A vital element of a mass storage system is the disks: in our system they will be one of the most expensive items. They are also one of our most-studied components.
Preliminary results of a performance study are available in Disk performance comparisons. The data layout is described here.
An initial suprise to many people is that we are focusing on EIDE disks, when conventional wisdom holds that SCSI disks have better performance. The reason is the price/performance ratio between the two interface types. Most disk drives are available with either EIDE or SCSI interfaces, with the SCSI interface model commanding between a $100 and %40 premium. Since the physical structure of the drives and heads is identical, the sustained I/O performance is nearly the same.
SCSI disks have the advantage of "tagged command queueing" and "disconnects", but these feature are often outweighed by the lower overhead of issuing IDE commands, and having few devices on an IDE chain.
A major advantage of a SCSI interface, the ability to connect many devices to single interface, is also not significant in this application: to use the I/O bandwidth of all connected devices limits the SCSI bus to just a few devices.
A final consideration is the cost of the SCSI adapter and cables. High performance SCSI adapters are expensive compared to bus-mastering EIDE adapters. And the cables for a high-performance SCSI bus, "ultra-wide, fast, differential" are a significant fraction of the disk drive price.
(Section omitted until after the preliminary design review in late March 1997.)
This project is funded by the DARPA Information Technology Office and the NASA HPCC program.