HP ProLiant ML570 G4 Server - Manual (Page 46)

Hardware options installation 46
After installing DIMMs, use RBSU to configure the system for online spare memory support.
Hot-plug mirrored memory
Hot-Plug mirrored memory (mirrored memory) provides a higher level of memory protection than either
Advanced ECC or Online Spare Memory. With mirrored memory, the server is protected against
uncorrectable memory errors that would otherwise result in server failure. Mirrored memory allows the
server to keep two copies of all memory data on separate memory boards.
If an uncorrectable error is encountered, the proper data is retrieved from the memory board that does not
contain the error. In addition, mirrored memory allows failed or degraded DIMMs to be replaced while
the server is running without requiring server downtime. The memory board with the failed DIMM(s) can
be removed, failed DIMMs replaced, and the board re-inserted into the server without any interruption to
the OS.
Mirrored memory is supported with either two or four memory boards installed. No OS support is
required.
Mirrored memory has two configurations: dual-board and quad-board. Single-board mirrored memory is
not supported. For either mode, choose "Mirrored" in RBSU.
The following guidelines apply to mirrored memory:
• All general memory requirements apply (" Memory board LEDs and components " on page 17 ).
• Mirrored memory is supported with two or four memory boards.
• Memory boards 1 and 2 are populated for dual-board mirrored memory. Boards 1, 2, 3, and 4 are
populated for quad-board mirrored memory. Any deviation from these guidelines results in the server
booting in Advanced ECC mode and Advanced ECC guidelines apply.
• Memory boards 1 and 2 form a mirrored pair for dual-board mirrored memory. For quad-board
mirrored memory, memory boards 3 and 4 form an additional mirrored pair.
• Memory boards within a mirrored pair must have the same amount of total memory. However, each
board of the mirrored pair may have different DIMM configurations as long as they have equal total
size. For example, memory boards 1 and 2 could each contain 2 GB of physical memory per board
with board 1 containing two 1-GB DIMMs and board 2 containing four 512-MB DIMMs.
• The amount of memory between mirrored pairs can be different in quad-board mirrored memory
mode. For example, memory pair 1 (boards 1 and 2) can contain 2 GB each while memory pair 2
(boards 3 and 4) contain 4 GB each.
• In quad-board mirrored memory, the two pairs of memory boards operate independently. One of the
pairs of memory boards can be degraded while the other pair of memory boards can still be fully
mirrored.
• Hot-add operations are not permitted. Board removals and insertions in mirrored memory are solely
for the purpose of hot-replace operations.
• For hot-replace to function properly, the memory board must be re-inserted into the location from
which it was removed. If the board is placed into the incorrect slot (for example, if board 2 is
removed in dual-board mirroring mode and re-inserted into memory slots 3 or 4), a configuration
error occurs. Attempting to insert a board into the improper position results in audio alarms and
visual alerts.
• Replace only one board at a time. That is, if memory boards 2 and 4 both contain memory errors,
remove board 2, replace the failed DIMMs, and replace board 2 before proceeding to board 4.
• If a board is inserted into a valid memory slot but with an invalid DIMM configuration (including too
much or too little memory), a DIMM configuration error occurs and a visual alert occurs. Refer to
Memory Board LEDs ("
Memory board LEDs and components " on page 17 ).
• If you remove a board while the server is running and do not replace the board, the next reboot
results in the system defaulting to Advanced ECC and Advanced ECC guidelines apply.