HP ProLiant DL980 DL980 G7 Maintenance & Service Guide - Page 48
Mirrored Memory population guidelines, Installing memory, GB DIMM pair in 1A/8A 1 GB.
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rank size of a 4-GB DIMM in pairs B, C, or D would be larger (2 GB) than the spare rank size of the 2-GB DIMM pair in 1A/8A (1 GB). Mirrored Memory population guidelines Errors that are not corrected by ECC or SDDC cannot be corrected by Online Spare memory. By providing added redundancy in the memory sub-system, Mirrored Memory provides the greatest protection against memory failure beyond ECC, SDDC, and Online Spare memory. In Mirrored Memory mode, each Lockstep DIMM pair of a memory controller (of a memory cartridge connected to a processor) has a mirrored DIMM pair on the other memory cartridge of the sibling processor in the same QPI island. Upon detecting an uncorrectable memory error from a DIMM pair of a memory cartridge, the processor avoids a system crash by reading the mirrored DIMM pairs from the other memory cartridge. In this case, the system management routine disables the failed DIMM. Further memory reads and writes will only occur on the mirrored DIMM pairs. The exceptions to Mirrored Memory mode are the following: • In Mirrored Memory mode, half of the memory is allocated to memory protection. • The available memory bandwidth is reduced by up to 50% in this mode. • Mirrored Memory mode, Online Spare mode, Hemisphere mode, and interleaving cannot be enabled simultaneously. To configure memory for Mirrored Memory mode, observe these additional constraints: • For the server to support Mirrored Memory, all processors must have a valid mirroring configuration. • The minimum allowable configuration is two memory cartridges per processor. • Both memory cartridges for each processor must be populated with the same DIMM configurations. • Although this configuration requirement is the same for Hemisphere mode and Mirrored Memory mode, only one of the two modes can be enabled at a given time. • Both of the CPU sockets on the same QPI island must be loaded with identical memory. Installing memory 1. Power down the server (on page 26). 2. Remove the processor memory drawer (on page 29). 3. Remove the memory cartridge ("Memory cartridge" on page 33). Illustrated parts catalog 48