HP ProLiant 1500 SMART-2DH Array Controller Reference Guide - Page 147

D-14 Understanding Drive Arrays ECC Memory To assure further data integrity, the Array Accelerator cache is made up of ECC memory. ECC (Error Checking and Correcting) memory will detect and correct all single-bit memory errors in multiple DRAMs. It will also detect all two-bit memory errors in any position and most three- and four-bit memory errors in a single DRAM. An entire DRAM can also fail without data loss. This ensures the correction of common memory errors without interrupting system operation. Batteries The Array Accelerator contains batteries that maintain any data cached there if a system power failure occurs. The batteries can preserve data in the Array Accelerator for up to four days. When power is restored to the system, an initialization feature writes the preserved data to the disk drives. The cells used in the Array Accelerator batteries are recharged via a "trickle" charge applied while system power is present. If posted writes were stored in the memory of the Array Accelerator and power loss occurs, you must reinstate power within approximately four days or the data stored in the memory will be lost. Note that this depends on the present condition of the Array Accelerator batteries. If you feel this risk is too great, you can disable the Array Accelerator. IMPORTANT: It is possible for the batteries to be depleted when you install a new SMART-2DH Controller. It can take up to 36 hours of system operation to charge the batteries fully. In this case, only the Array Accelerator is affected; your system will continue to run without interruption. During Power-On Self-Test (POST), the SMART-2DH Controller checks the batteries. If the battery charge is low or depleted, a 1794 POST error message is displayed indicating that the Array Accelerator is disabled. The controller temporarily disables the Array Accelerator until the batteries reach 90 percent charge. The board continues to function properly, at a slightly lower performance, until the batteries reach 90 percent charge. At this point, the Array Accelerator is automatically enabled. Writer: Pamela King Project: SMART-2DH Array Controller Reference Guide Comments: 295469-002 File Name: K-APPD.DOC Last Saved On: 2/27/98 12:06 PM COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED