NCR Corp, one of the pioneers of redundant arrays of inexpensive disks, has come out with an SCSI disk array controller board, the ADP-92-06, which it says enable designers to bring high availability storage products to market more quickly for AT and EISA bus personal computers. The ADP-92-06 is capable of managing an array of up to 35 SCSI disk drives in RAID 0, 1, 3 and 5.RAID 0 is data striping without parity for high performance, but no increase in data availability. RAID 1 is a mirrored disk array, writing every block to both the data disk and mirror disk. RAID 3 is a parallel disk array using several drives in even numbers acting as a large virtual drive with high bandwidth – two or more times that of a conventional drive. One drive is dedicated to parity information storage. RAID 3 is suited to large block transfers. And RAID 5 is an independent disk array, with parity spread across all the drives – which are still mirrored, so that there is no problem if the parity drive fails. The ADP-92-06 also offers the highest level of integration in the industry; it uses the 25MHz Motorola Inc 68EC020 32-bit microprocessor, and is designed to transfer data at 20Mbytes per second via a high-bandwidth SCSI-2 channel connection to the host system. It supports intelligent request queue management; tagged and untagged queued command support; simultaneous request servicing; multiple logical units per rank of drives; ranks of concurrent combinations of RAID levels 0, 1, 3, and 5; synchronised spindle support; programmable striping size; remote firm ware update; on-line data reconstruction for replacement of failed disk; end-to-end error detection on all internal data paths; and built-in diagnostics. The OEM list price for the ADP-92-06 disk array controller is $2,000, and evaluation boards will be offered in November.
