IBM 88784RU User Manual

Also see for x3950 8872: Installation guide

Contents

The following notes describe the Active Memory features:v Memory mirroring enables you to improve the reliability of the memory in yourserver by creating a mirror of the data in memory port 1 and storing it in memoryport 2.Note: For memory mirroring to work, you must have DIMMs of the same sizeand clock speed in both memory ports.Complete the following steps to enable memory mirroring:1. Check your operating system documentation to make sure that it supportsmemory mirroring.2. Install DIMMs of the same size and clock speed in the two memory ports.3. Enable memory mirroring in the Configuration/Setup Utility program:a. Turn on the server and watch the monitor screen.b. When the message Press F1 for Configuration/Setup appears, pressF1.c. From the Configuration/Setup Utility main menu, select Advanced Setup.d. Select Memory Settings.e. Select Memory Mirroring Settings.f. Enable the memory mirroring setting from within this window.g. Save and exit the Configuration/Setup Utility program.When memory mirroring is enabled, the data that is written to memory is storedin two locations. One copy is kept in the memory port 1 DIMMs, while a secondcopy is kept in the memory port 2 DIMMs. During the execution of the readcommand, the data is read from the DIMM with the least number of reportedmemory errors through memory scrubbing, which is enabled with memorymirroring.If memory scrubbing determines that a DIMM is damaged beyond use, read andwrite operations are redirected to the remaining good DIMMs. Memory scrubbingthen reports the damaged DIMM and light path diagnostics displays the error.After the damaged DIMM is replaced, memory mirroring then copies the mirroreddata back into the new DIMM.v Memory scrubbing is an automatic daily test of all the system memory thatdetects and reports memory errors that might be developing before they cause aserver outage.Note: Memory scrubbing and Memory ProteXion technology work with eachother and do not require memory mirroring to be enabled to work.When an error is detected, memory scrubbing determines whether the error isrecoverable. If it is recoverable, Memory ProteXion is enabled and the data thatwas stored in the damaged locations is rewritten to a new location. The error isthen reported so that preventive maintenance can be performed. Provided thatthere are enough good locations to enable the correct operation of the server, nofurther action is taken other than recording the error in the error logs.If the error is not recoverable, memory scrubbing sends an error message to lightpath diagnostics, which lights LEDs to guide you to the damaged DIMM. Ifmemory mirroring is enabled, the mirrored copy of the data in the mirrored DIMMis used to refresh the new DIMM after it is installed.v Memory ProteXion reassigns memory bits to new locations within memory whenrecoverable errors have been detected.34 IBM System x3950 Type 8872 and System x3950 E Type 8874: User’s Guide