HP 166207-B21 Smart Array 5300 Controller User Guide - Page 18

Board Components and Features For each of these operations, data has to be reorganized among hard drives, and must be saved to non-volatile storage during the operation. (For further details of these operations, refer to Chapter 7, Appendix D, and Appendix E.) Without batterybacked cache, the data can only be stored at empty locations within the drive array, so these operations cannot occur at all if the array is full. If the array controller or server fails before cached data can be stored on the array, the array accelerator and its integrated batteries may be removed from one array controller and installed on another controller of the same type. Any data in the array accelerator that has not been written to the hard drive will be transferred to the other array controller. Other features of the array accelerator include: • Cache capacity of 96-MB or 224-MB (32 MB of the cache is used for transfer buffer) • Adjustable read/write ratio (usually set during array configuration as described in Chapter 7, but can be changed at any time) • Error checking and correcting (ECC) memory, providing single-bit data correction Sometimes, the Automatic Performance Tuning feature disables the array accelerator. You can also disable the array accelerator manually through the Array Configuration Utility (refer to Chapter 7 for details). Batteries The array accelerator cache has two rechargeable and replaceable NiMH battery packs. If the array accelerator is removed from the array controller, the battery packs maintain any cached data on the array accelerator for up to four continuous days. 1-6 Compaq Smart Array 5300 Controller User Guide