Redundant arrays of IDE drives

We report tests of redundant arrays of IDE disk drives for use in offline high energy physics data analysis. Parts costs of total systems using commodity EIDE disks are now at the $4000 per Terabyte level. Disk storage prices have now decreased to the point where they equal the cost per Terabyte of Storage Technology tape silos. The disks, however, offer far better granularity; even small institutions can afford to deploy systems. The faster access of disk versus tape is an added bonus. Our tests include reports on software RAID-5 systems running under Linux 2.4 using Promise Ultra 100™ disk controllers. RAID-5 protects data in case of a single disk failure by providing parity bits. Tape backup is not required. Journaling file systems are used to allow rapid recovery from crashes. We also report on using FireWire to PCI interfaces. Our data analysis strategy is to encapsulate data and CPU processing power. Data is stored on many PCs. Analysis for a particular part of a data set takes place on the PC where the data resides. The network is only used to put results together. We explore three methods of moving data between sites; internet transfers, hot pluggable IDE disks in FireWire cases, and DVD-R disks.