The IBM Corp mainframe world has been waiting for a disk array subsystem from Hitachi Ltd for some time, and it has now arrived – but Comparex Informationssysteme GmbH got in with the announcement first. Comparex calls the subsystem the Tetragon 2000, and highlights the fact that the subsystem does not need to be taken off-line for component replacement, feature implementation, capacity upgrade or installing a new release of the microcode. It is designed to eliminate any single point of failure, and has 256Mb to 8Gb of non-volatile cache. A Mirrored Cache feature enables users to maintain a copy of Fast Write data in the cache. The Tetragon is built up of groups of seven 3.5 dual-ported fast and wide SCSI-2 disk drives, six for data, the seventh for parity, and spare drives can be installed that can tbe addressed dynamically if the user requires that level of resilience. The subsystems each store 22.7Gb, and a minimum configuration has one, a maximum has 32 for 724Gb maximum capacity. The Tetragon supports two or four Channel Adaptor Processors, each with two internal 200M-byte per second buses, and each providing four paths to each host processor. It also supports two to eight Disk Adaptor Processors, each with four SCSI interfaces for up to 32 concurrent back-end operations. Up to 16 parallel or serial host attachments are supported with maximum speed of 17M-bytes per second. It will ship in the third quarter.
