Dell POWEREDGE 1955 - Manual (Page 79)

Installing System Options
79
The following guidelines apply to memory sparing:
• The system only supports memory sparing if eight identical memory modules are installed (same size,
speed, technology, and vendor).
• Sparing is not supported if mirroring is enabled.
You can enable memory sparing through the System Setup program. See "Using the System Setup
Program" on page 43.
Memory Mirroring
Memory mirroring provides additional data redundancy and system availability. The system divides the total
memory in half and copies identical sets of data to each half. Consequently, the amount of available
memory is half the amount of physical memory. If a memory module fails, the data in the mirrored data set
is still available, and the system can operate normally until the memory module is replaced.
The following guidelines apply to memory mirroring:
• The system only supports memory mirroring if eight identical memory modules are installed.
• Mirroring is not supported if sparing is enabled.
You can enable memory mirroring through the System Setup program. See "Using the System Setup
Program" on page 43.
Table 3-1. Memory Sparing Configurations
Memory Module Size/Type Total Memory Available Memory Spare Memory
Eight 256-MB single-rank modules 2 GB 1 GB 1 GB
Eight 512-MB single-rank modules 4 GB 2 GB 2 GB
Eight 1-GB single-rank modules 8 GB 4 GB 4 GB
Eight 2-GB single-rank modules 16 GB 8 GB 8 GB
Eight 2-GB dual-rank modules 16 GB 12 GB 4 GB
Eight 4-GB dual-rank modules 32 GB 24 GB 8 GB