HP ProLiant ML570 G4 Server - Manual (Page 47)

Hardware options installation 47
Hot-plug RAID memory
Hot-plug RAID memory (RAID memory) provides a similar level of memory protection as mirrored memory
but obtains this protection using less total memory. For example, in a RAID memory configuration, 25% of
the installed memory is not available to the OS. In a mirrored memory configuration, however, 50% of the
installed memory is not available to the OS. RAID memory protects the server against uncorrectable
memory errors that would otherwise result in a server failure.
Although mirrored memory keeps two copies of all memory data, RAID memory keeps only one copy of
all memory data and additional parity information. If an uncorrectable memory error is encountered, the
server can create the proper data using the parity information and the information from the other memory
boards that contain no failures.
As with mirrored memory, RAID 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.
RAID memory is only supported if all four memory boards are installed. No OS support is required.
The following guidelines apply to Hot-Plug RAID memory:
• All general memory requirements apply (" Memory board LEDs and components " on page 17 ).
• RAID memory is only supported with four memory boards.
• All four memory boards must have the same amount of total memory. However, each board may
have different DIMM configurations as long as they have equal total size. Any deviation from this
rule results in the server booting in Advanced ECC mode and Advanced ECC guidelines apply.
• No hot-add operations are supported in RAID memory, only hot-replace.
• If you remove a board while the server is running and do not replace it, the next reboot results in the
system reverting to Advanced ECC and Advanced ECC guidelines apply.
Memory boards and DIMMs
NOTE: The ProLiant ML570 G3/G4 memory board operates at different front-side bus speeds:
• In HP ProLiant ML570 Generation 4 Servers, the G3/G4 memory board operates at 667 MHz
or 800 MHz, depending on the front-side bus speed of the installed processor.
• In HP ProLiant ML570 Generation 3 Servers, the G3/G4 memory board operates at 667 MHz
with no performance gain over ProLiant ML570 G3 memory boards.
IMPORTANT: Installing a ProLiant ML570 G3 memory board in an HP ProLiant ML570 G4 Server forces
the front-side bus speed to 667 MHz. If the installed processor has an 800-MHz front-side bus, a message
displays at POST.
IMPORTANT: The HP ProLiant ML570 G4 Server does not support hot-add of ProLiant ML570 G3 memory
boards. Inserting the memory board generates an audio alert and the memory board LEDs flash. The
memory board does not power up. The board can be removed without powering down the server.
Memory board and DIMM installation, removal, and replacement procedures can be either hot-plug or
non-hot-plug, depending on how the server is configured. Hot-plug operations can be hot-add or hot-
replace. Hot-add makes additional memory resources available to the OS. Hot-replace allows failed or
degraded DIMMs to be replaced while the server is running. Hot-add is only supported with Microsoft®
Windows® 2003 or later. Hot-replace has no OS requirements.
The following table illustrates AMP modes that support hot-plug features.