HP Integrity rx4640 Server - Manual (Page 17)

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 6, Appendix D, and Appendix E.) Without battery-
backed 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 6, “Configuring an Array,” 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 6, “Configuring an Array,” 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 HP Smart Array 5300 Controller User Guide
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