HP ProLiant BL420c Gen8 Server Blade - Manual (Page 32)

Hardware options installation 32
is degrading. This allows DIMMs that have a higher probability of receiving an uncorrectable memory
error (which would result in system downtime) to be removed from operation.
Advanced Memory Protection options are configured in RBSU. If the requested AMP mode is not supported
by the installed DIMM configuration, the server blade boots in Advanced ECC mode. For more information,
see "HP ROM-Based Setup Utility (on page 56 )."
The server blade also can operate in independent channel mode or combined channel mode (lockstep).
When running in lockstep mode, you gain reliability in one of two ways:
• If running with UDIMMs (built with x8 DRAM devices), the system can survive a complete DRAM failure
(SDDC). In independent channel mode, this failure would be an uncorrectable error.
• If running with RDIMM (built with x4 DRAM devices), the system can survive the complete failure of two
DRAM devices (DDDC). Running in independent mode, the server can only survive the complete failure
of a single DRAM device (SDDC).
Maximum capacity
DIMM type DIMM rank One processor Two processors
RDIMM Single-rank 48 GB 96 GB
RDIMM Dual-rank 96 GB 192 GB
LRDIMM Quad-rank 192 GB 384 GB
UDIMM Single-rank 12 GB 24 GB
UDIMM
Dual-rank 48 GB 96 GB
For the latest memory configuration information, see the QuickSpecs on the HP website
( http://www.hp.com ).
Advanced ECC memory configuration
Advanced ECC memory is the default memory protection mode for this server blade. Standard ECC can
correct single-bit memory errors and detect multi-bit memory errors. When multi-bit errors are detected using
Standard ECC, the error is signaled to the server blade and causes the server blade to halt.
Advanced ECC protects the server blade against some multi-bit memory errors. Advanced ECC can correct
both single-bit memory errors and 4-bit memory errors if all failed bits are on the same DRAM device on the
DIMM.
Advanced ECC provides additional protection over Standard ECC because it is possible to correct certain
memory errors that would otherwise be uncorrected and result in a server blade failure. Using HP Advanced
Memory Error Detection technology, the server blade provides notification when a DIMM is degrading and
has a higher probability of uncorrectable memory error.
Online Spare memory configuration
Online spare memory provides protection against degraded DIMMs by reducing the likelihood of
uncorrected memory errors. This protection is available without any operating system support.
Online spare memory protection dedicates one rank of each memory channel for use as spare memory. The
remaining ranks are available for OS and application use. If correctable memory errors occur at a rate
higher than a specific threshold on any of the non-spare ranks, the server blade automatically copies the
memory contents of the degraded rank to the online spare rank. The server blade then deactivates the failing
rank and automatically switches over to the online spare rank.