HP ProLiant SL250s Gen8 Server - Manual (Page 41)

Hardware options installation 41
is degrading. This enables DIMMs that have a higher probability of receiving an uncorrectable memory
error (which results in system downtime) to be removed from operation.
The server also can operate in independent channel mode or combined channel mode (Lockstep Memory
mode). When running in Lockstep Memory 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).
Advanced Memory Protection options are configured in RBSU. If the requested AMP mode is not supported
by the installed DIMM configuration, the server boots in Advanced ECC mode. For more information, see
"HP ROM-Based Setup Utility (on page 87 )."
Maximum memory configurations
The server supports a maximum of 256 GB of memory with one processor (8 x 32 GB), or 512 GB of memory
with two processors (16 x 32 GB).
Advanced ECC memory configuration
Advanced ECC memory is the default memory protection mode for this server. 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 and causes the server to halt.
Advanced ECC protects the server 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 failure. Using HP Advanced
Memory Error Detection technology, the server 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 automatically copies the memory
contents of the degraded rank to the online spare rank. The server then deactivates the failing rank and
automatically switches over to the online spare rank.
Lockstep memory configuration
Lockstep mode provides protection against multi-bit memory errors that occur on the same DRAM device.
Lockstep mode can correct any single DRAM device failure on x4 and x8 DIMM types. The DIMMs in each
channel must have identical HP part numbers.
Maximum capacity