HP Surestore Disk Array 12h SGI IRIX Configuration Guide - Page 67

ACA ACP AL AL-PA allocation array group BC BS BTU °C CA ca cache GLOSSARY HP Surestore Asynchronous Continuous Access XP. Array control processor. The ACP handles the passing of data between the cache and the physical drives held in the DKUs. ACPs work in pairs, providing a total of 8 SCSI buses. Each SCSI bus associated with one ACP is paired with a SCSI bus on the other ACP pair element. In the event of an ACP failure, the redundant ACP takes control. Both ACPs work together sharing the load. Arbitrated loop. Arbitrated loop physical address. The ratio of allocated storage capacity versus total capacity as a percentage. Allocated storage refers to those LDEVs that have paths assigned to them. The allocated storage capacity is the sum of the storage of these LDEVs. Total capacity refers to the sum of the capacity of all LDEVs on the disk array. The number of physical disk drives contained in a RAID group. This number depends on the RAID configuration. For example, there may be two or four physical disks in a RAID1 group. There are four physical disks in a RAID5 group. The HP Surestore Business Copy XP software program that lets you maintain up to nine internal copies of logical volumes on the disk array. Basic supply. British thermal unit. Degrees centigrade/Celsius. The HP Surestore Continuous Access XP software program that lets you create and maintain duplicate copies of the data store on a local disk array. Cache. Very high speed memory that is used to speed I/O transaction time. All reads and writes to the XP array family are sent to the cache. The data is buffered there until the transfer to/from physical disks (with slower data throughput) is complete. The benefit of cache memory is that it speeds I/O throughput to the application. The larger the cache size, the greater the amount of data buffering that can occur and the greater throughput to the applications. 67