Patent Publication Number: US-2007101191-A1

Title: Memory dump method, computer system, and memory dump program

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a memory dump method, a computer system, and a memory dump program and, more particularly, to a memory dump method, a computer system, and a memory dump program capable of reducing down time of a system by using a small number of hardware (memory) components when a system crash occurs in the system.  
      Conventionally, a memory dump is obtained when a system crash occurs, and the system is rebooted after the memory dump is obtained.  
      Consequently, in the related memory dump, there is a problem that if a system crash occurs in a computer system containing very large memory, system down time increases because it takes a large amount of time for obtaining a memory dump.  
      As a measure against the problem, Japanese Patent Laid-Open No. 2004-102395 discloses a related method. In this method, the information processing system has duplicated memories, the same data is always held in both memories. In occurrence of the failure, data required for rebooting the information processing system is loaded in one of the memories to reboot the information processing system, and memory data is held in the other memory as memory dump data for the failure occurrence. In this way, down time of the system can be reduced and memory dump data can be obtained after rebooting the system. However, this related method has a problem that two memory, one of which is for loading data required for rebooting and the other of which is for holding memory dump data, are needed for each system.  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to provide a memory dump method, a computer system, and a memory dump program capable of reducing down time of a system by using a small number of hardware (memory) components when a system crash occurs in the system.  
      According to one aspect of the present invention, a memory dump method in a computer system in which a partition is configured by combining any number of cells with any number of input and output sections, wherein said cell consists of a CPU and a memory, the memory dump method comprising: disconnecting said cell constituting said partition in which a system crash has occurred, if any of said partitions shuts down because of said system crash, from said partition with memory information in said memory being held; setting a spare cell, which does not belong to any of said partitions, in said partition in which a system crash has occurred; booting said computer system; and writing said memory information contained in said memory in said disconnected cell onto a recording medium after booting said partition which has shut down because of said system crash.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other features and advantages of the invention will be made more apparent by the following detailed description and the accompanying drawings, wherein:  
       FIG. 1  is a block diagram showing a main portion of a computer system according to one embodiment of the present invention;  
       FIG. 2  is a flowchart of an operation performed when a system crash occurs in partition P 1 ; and  
       FIG. 3  is a flowchart of an operation performed to reboot partition  1 .  
      In the drawings, the same reference numerals represent the same structural elements. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A first exemplary embodiment of the present invention will be described in detail below.  
      Referring to  FIG. 1 , a computer system according to the exemplary embodiment includes crossbar  10  capable of flexibly connecting any of cells  1 ,  2 , and  3  to any of Input/Output (IO) sections  11  and  12 . Cell  1  includes CPU  4  and memory  7 . Cell  2  includes CPU  5  and memory  8 . Cell  3  includes CPU  6  and memory  9 . The computer system in the present embodiment has the following two partitions. Partition P 1  includes cell  1  and IO section  11 . Partition P 2  includes cell  2  and IO section  12 . Partitions P 1  and P 2  operate on different Operating Systems (Oss), respectively. Cell  3 , which includes CPU  6  and memory  9 , is a spare cell which does not belong to any of partitions P 1  and P 2 , when the system starts the operation. It should be noted that one partition may include any number of IO sections and cells. Also, any number of spare cells may be provided with the computer system.  
      Dump read/write control section  13  reads memory information from memory  7  in cell  1 , memory  8  in cell  2 , or memory  9  in cell  3 . Dump read/write control section  13  writes the memory information onto dump disk  14  by an instruction from service processor  15 . Dump disk  14  may be any storage, for example, a hard disk on which information can be recorded.  
      Service processor  15  monitors whether a system crash has occurred in any of partitions  1  and  2 . Service processor  15  has system crash flags  161  and  162  indicating whether a system crash has occurred in partitions  1  and  2 , respectively. If a system crash occurs, system crash flag  161  or  162  is set to  1 ; if no system crash has occurred, system crash flags  161  and  162  are set to 0. Service processor  15  also controls how partitions P 1  and P 2  are to be configured with cells  1 ,  2  and  3  and IO sections  11  and  12  (partition configuration control) In particular, when service processor  15  recognizes that any of system crash flags  161  or  162  is changed from  0  to  1  due to a system crash, service processor  15  disconnects cell  1  in partition P 1  or cell  2  in partition P 2  in which the system crash has occurred and sets in spare cell  3  into the configuration. Service processor  15  also issues an instruction to initialize memory  9  in spare cell  3  included in partition P 1  or P 2  and issues an instruction to boot OS in partition P 1  or P 2 .  
      In order to deal with a system crash which has occurred in both partitions P 1  and P 2  at a time; the number of spare cells  3  must be greater than or equal to the total of the number of cells in partition P 1  and the number of cells in partition  2 . In the present embodiment, partition  1  includes one cell and partition  2  also includes one cell, therefore two or more spare cells  3  are needed.  
      An operation of the present embodiment will be described below.  
       FIG. 2  is a flowchart of an operation performed if a system crash occurs in partition P 1 . The OS is preset such that a memory dump is not obtained when a system crash occurs. If a system crash occurs in partition P 1  consisting of cell  1  and IO section  11 , service processor  15  detects the system crash in partition P 1  (step  101 ) and sets system crash flag  161  in service processor  15  (step  102 ). At the same time, service processor  15  holds the memory information contained in memory  7  in cell  1  belonging to partition P 1  (step  103 ). Because it is preset on OS that a memory dump is not obtained when a system crash occurs, partition P 1  consisting of cell  1  and IO section  11  shuts down the OS without obtaining a memory dump (step  104 ).  
      An operation performed for rebooting partition P 1  will be described next.  
       FIG. 3  is a flowchart of an operation performed for rebooting partition P 1 . Service processor  15  checks whether system crash flag  161  is set (step  201 ). If not, service processor  15  initializes memory  7  of cell  1  (step  202 ). Service processor  15  then boots the OS in partition P 1  consisting of cell  1  and IO section  11  (step  203 ).  
      On the other hand, if system crash flag  161  in service processor  15  is set, service processor  15  instructs crossbar  10  to disconnect cell  1  which constitutes partition P 1 . In response to the instruction from service processor  15 , crossbar  10  disconnects cell  1  constituting partition P 1  and sets in cell  3  provided beforehand as a spare cell which does not belong to any of partitions P 1  and P 2  (step  204 ) into partition  1 . New partition P 1  is denoted by partition P 11 .  
      Then, when recognizing that setting in cell  3  is completed and new partition P 1  (partition P 11 ) is configured, service processor  15  initializes memory  9  of cell  3  which constitutes partition P 1  (partition P 11 ) (step  205 ). Service processor  15  then boots the OS in new partition P 1  (partition P 11 ) consisting of cell  3  and IO section  11  (step  206 ).  
      Then, in response to an instruction from service processor  15 , dump read/write control section  13  reads the memory information from memory  7  of cell  1  constituting partition P 1  at the time the system crash occurred and writes it on dump disk  14  (step  207 ). On notification by dump read/write control section  13  of completion of writing to dump disk  14 , service processor  15  clears system crash flag  161  (step  208 ).  
      Similar operation in partition P 2  is performed if a system crash occurs in partition P 2 . Cell  2  constituting partition P 2  is disconnected from partition P 2  and cell  3  provided beforehand as a spare cell is set in to produce a new partition P 2  (partition P 21 ). Then, service processor  15  boots the OS in the new partition P 2  (partition P 21 ) and obtains a memory dump.  
      A first effect of the present invention is that because memory information in a cell constituting a partition is held if a system crash occurs in the partition and the cell is replaced with a spare cell that does not belong to any partitions to reboot the OS, the OS can be rebooted without obtaining a memory dump after the system crash occurs, thereby reducing the down time.  
      A second effect of the present invention is that failure diagnosis can be surely executed because memory information in a partition where a system crash has occurred is saved and, after rebooting the OS, the memory information is obtained and stored on a dump disk.  
      A third effect of the present invention is that a spare cell to be replaced with a cell in the event of a system crash can be used for any of partitions and a spare cell does not need to be provided for each partition because a computer system is used in which any of cells and IO sections can be flexibly combined to configure a partition.  
      The configuration of partitions and the number of partitions and spare cells are not limited to those in the present invention.  
      Furthermore, processes described with respect to  FIGS. 2 and 3  may be performed by a computer program.