SGI Challenges at D0

What is an SGI Challenge?

In the first approximation it is a multiprocessor system based on MIPS R4400MC 64-bit RISC CPUs with very high I/O bandwidth, capable of delivering data in excess of 320 Mbytes/second. We have two Challenges, d0cha and d0chb, for D0 users. They are both Challenge XL systems.

d0cha is used mainly as PIAF server. It has twelve processors each running at 150MHz and 1536 Mbytes of shared memory expandable up to 6 Gbytes.

d0chb is used mainly as interactive/small batch system. It has eight 200MHz CPUs and 768 Mbytes of shared memory.

Each processor in all three Challenges has 16 Kbytes on-chip instruction cache, 16 Kbytes on-chip data cache, and 1 Mbyte of a secondary cache. The processors inside each Challenge system can communicate amongst themselves over a high performance system bus with a bandwidth of 1.2 Gbyte/sec.

For each Challenge, High-Speed I/O system can deliver data rate up to 320 Mbytes/sec. In addition there is a VME64 bus with a bandwidth of 50 Mbytes/sec. Each system can handle up to 24 SCSI-2 channels (with up to 15 devices per channel) with a maximum bandwidth of 20 Mbytes/sec per channel.

Why Challenge?

Challenge is an example of a class of strongly coupled computer systems: it consists of an expandable collection of high performance processors, accessing a very large data set locally, i.e. without any local area network. Other systems of this type include: DEC Sables, Convex Exemplar, IBM SP1/SP2 systems. The SGI Chalenge was selected because of its high performance/price ratio. An additional argument that our D0 software is already ported to the SGI platform was of importance too.

What for?

• Central Analysis Engine: taking advantage of very high I/O bandwidth all jobs requiring access to a very large data sets should run efficiently there
• UNIX-based File Server (or Event Server, or Object Server) delivering smaller data sets to the analysis clusters located at D0.
• Unexpected: if the system performs anywhere near expectations, many of us will find multiple uses of it for our favoured physics projects. Looking forward....

Disks Available