HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 269

Glossary Glossary Secondary Array Controller Self Configuring Self-test Shutdown In disk arrays with two controllers, one controller is called the Primary Array Controller and the other is called the Secondary Array Controller. The Secondary Array Controller offers redundant controller operation should the primary array controller ever fail. The Secondary Array Controller offers redundant controller operation (full access to all data) and it also monitors the status of the Primary Array Controller. If the status of the Primary Array Controller is ever questionable, the Secondary Array Controller is able to become the Primary Array Controller. The Secondary Array Controller can also improve the performance (throughput) of the disk array (host-dependent). No RAID knowledge is required to use the disk array, since the logistics of RAID are all managed by the Disk Array Controller. Self-test is an internal diagnostic test sequence that is performed whenever the power is switched on. The results of the Self-test, pass or fail, are displayed by a status light on the front panel of each device. Shutdown is a coordinated process of taking the disk array offline. During a Shutdown, vital configuration information is copied from the array controller NVRAM to the disks. This provides more permanent storage for this information. In the shut down state, the disk array can still execute some SCSI commands from the host, but the host cannot access any data on the array. SIMMs The disk array allows a total of three 32-Megabyte SIMMs on the Disk Array Controller. The maximum capacity is therefore 96 Megabytes. The SIMMs provide Error Correction Code (ECC). Status Light Stripe Depth The Status Light is a light on the front panel of each disk module, power module, and fan. The status light is used to indicate normal operating conditions and fault conditions of a particular device. The Stripe Depth used by the disk array in RAID 5 mode is 64K blocks. Normally, RAID 5 mode incurs a performance penalty, since in order to determine the proper parity, previously- written data must be read. This is called the read/modify/write penalty. However, when the data to be written exceeds the size of the stripe depth, or 64K, no read/modify/write penalty is incurred because all of the data (including parity) already exists in RAM. 269