HP ProLiant 2500 SMART-2DH Array Controller Reference Guide - Page 16

1-5 Wide-Ultra SCSI, Fast-Wide SCSI-2, and Fast-SCSI-2 The SMART-2DH Array Controller complies with ANSI SCSI-2 standards, supporting 16-bit Wide-Ultra SCSI, 16-bit Fast-Wide SCSI-2, and 8-bit FastSCSI-2 (standard SCSI) devices. Wide-Ultra SCSI Wide-Ultra SCSI technology provides SCSI data transfer rates of up to 40-Mbytes/sec at a 20-MHz bus rate. This combination allows high throughput in many network application environments, including resource sharing and database servicing. Fast-Wide SCSI-2 and Fast-SCSI-2 Fast-Wide SCSI-2 provides two bytes of data at each bus transfer, providing a maximum of 20-Mbytes/sec data rate between SCSI devices while still maintaining a 10-MHz bus rate. Compaq Fast-Wide SCSI-2 controllers and devices are able to communicate using Fast-SCSI-2 protocol when required. Therefore, Fast-SCSI-2 drives may also be used with SMART-2DH Array Controller using the appropriate cable adapter. Array Accelerator The SMART-2DH Controller Array Accelerator provides a 16-MB onboard write cache. The result is improved performance on data access to the drive array by serving as a posted-write cache and read-ahead cache. The write cache can accept data from the server at 60 megabytes per second. At the same time, read and writes caches can be accommodated by the drivers. The read-ahead cache uses a multi-threaded algorithm to predict the next likely read operation for the array. That data is then read into the Array Accelerator from the drives. When the SMART-2DH Array Controller receives a read request for the cached data, it can be brought immediately into system memory bus speeds. The Array Accelerator feature may be disabled by software if desired. SMART-2DH Array Controller Reference Guide Writer: Pamela King Project: SMART-2DH Array Controller Reference Guide Comments: 295469-002 File Name: B-CH01.DOC Last Saved On: 2/27/98 11:23 AM COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED