Patent Publication Number: US-2012036214-A1

Title: Alternative transfer of logical partitions (lpar) from one lpar computer system to another

Description:
TECHNICAL FIELD 
     The present invention relates to Logical Partitions (LPAR) computer systems and particularly to the transfer or migration of a LPAR from one computer system to another. 
     BACKGROUND OF RELATED ART 
     A Logical Partition (LPAR) is a portion of a computer system&#39;s physical resources virtualized to perform as a separate virtual computer in a LPAR computer environment. The LPAR unit determines its logical partitioning function and its mode of operation. Currently, LPAR implementations have been effectively used in server controlled computer systems, such as the pSeries Power systems. 
     Even relatively small server controlled systems host many LPARs. As the number of hosted LPARs increases, finding maintenance windows acceptable to all of the LPARs in a server controlled system becomes increasingly difficult. Thus, the ability to transfer, i.e. migrate, partitions between server controlled LPAR systems without disrupting the running of operating systems and hosted application programs has become an necessity. Such partition mobility allows users to distribute partitions between server systems so that previously disruptive operations may be performed on selective machines at the user&#39;s convenience rather than when such operations cause the least inconvenience to others. 
     A particularly effective form of LPAR mobility has been Live Partition Mobility developed by International Business Machines Corporation (IBM), which is described in the publication,  IBM PowerVM Live Partition Mobility , John E. Bailey et al, March 2009, which may be obtained at ibm.com/redbooks, particularly at pp. 1-14. This partition mobility permits the migration or transfer of partitions that are running AIX and Linux operating systems, including hosted applications from one physical server system to another without disrupting any infrastructure services. The migration transfers the whole partition system environment including the processor state, memory, attached virtual devices and connected users. Thus, systems partitions may undergo maintenance and modification without disruption. 
     While this capability to readily move partitions has given the information processing industry tremendous flexibility in balancing workload between server systems, it does require that the source and destination systems of the partition being transferred be able to access an external storage from which the mobile partition&#39;s operating system, applications and associated data are available. This external storage system and network has been standardized by the computer industry as the Storage Area Network (SAN) technology. The SAN is essentially a high speed special purpose network that interconnects a variety of storage devices associated with user server systems in support of the networks interconnecting the server systems. 
     While a great number of current LPAR systems do have access to SAN or like external storage networks, there remain many user LPAR system that do not have such access. The present invention offers the users of such LPAR systems, not connected to SAN, an alternative for the transfer of LPARs. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides an implementation for alternative migration of a LPAR from one server system to another when either or both of the server systems cannot access a SAN or like external storage network. 
     In its broadest aspect, the present invention involves an implementation for transferring a logical partition (LPAR) from a source server controlled computer system to a destination server controlled computer system over a connecting network that comprises first determining if the source server system and the destination server system have access to the same SAN. If both server systems have such access, then a standard live partition mobility transfer of the LPAR is made by transmitting the LPAR over the Ethernet, i.e. a connecting network such as the Internet, from the source server system to the destination server system along with transmitting all data storage supporting the LPAR from the source server system to the destination server system over the external SAN. 
     On the other hand, if the source and destination server system do not have access to the same SAN, then a mirror image of all data storage supporting the transferred LPAR is created and transmitted to local storage supporting the destination server system; then the LPAR is transmitted over the connecting network from the source server system to the destination server system. 
     In the implementation, the mobile LPAR is transmitted over the connecting network using iSCSI protocols and the mirror image of all data storage supporting said LPAR is transmitted over a network using iSCSI protocols. 
     As will be hereinafter set forth in greater detail, prior to the creating of the mirror image, it should be determined that said local storage supporting the destination server system is capable of storing the mirror image. Accordingly, a preferred implementation, upon a determination that the destination server has such supporting storage, comprises accessing by the destination server system using iCSCI protocols, the data storage at the source server supporting the transferred LPAR wherein the source server data storage is treated as a target device of the destination server; then, creating said mirror image and transmitting the mirror image over the network using said iSCSI protocols. 
     The present invention may be used for systems in which the source server and the destination server are Virtual I/O Servers (VIOS), as well as for systems in which the source and destination server systems are Central Electronics Complex (CEC) servers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art by reference to the following drawings, in conjunction with the accompanying specification, in which: 
         FIG. 1  is a generalized diagrammatic view of a network portion to illustrate the transfer of a mobile LPAR from one server system to another; 
         FIG. 2  is a generalized diagrammatic view of a network portion to illustrate the transfer of a mobile LPAR from one server system to another using the alternative transfer implementation of the present invention; 
         FIG. 3  is an illustrative simplified diagrammatic view of a control processor that may be used for the hypervisors of the server systems of  FIGS. 1 and 2 ; 
         FIG. 4  is a general flowchart of a program set up to implement the present invention for the transfer of a mobile LPAR from one server system to another using the alternative transfer implementation; 
         FIG. 5  is a general flowchart of a program set up to implement the present invention for the specific creation and transmission of the mirror image of the data storage of the LPAR being transferred; and 
         FIG. 6  is a flowchart of an illustrative run of the programs set up in  FIGS. 4 and 5  for the alternative LPAR transfer of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown a generalized diagrammatic view of a network portion illustrating the live transfer of a mobile LPAR  12  from a source server system  10  to a destination server system  11 . The system involved in this embodiment is the Power6™ System marketed by IBM as described in the above-mentioned publication,  IBM PowerVM Live Partition Mobility , John E. Bailey et al, March 2009, which may be obtained at ibm.com/redbooks, particularly at pp. 1-14. 
     The respective server operations are respectively controlled by Hypervisors  13  and  14  through their respective servers, VIOS partitions  15  and  16 , i.e. each of the source  10  and destination  11  systems is respectively configured with a single Virtual I/O Server partition  15  and  16 . The transfer of mobile partition  12  from system  10  to system  11  over an Ethernet  18 , such as the Internet, uses iSCSI protocols and is coordinated by Hardware Management Console (HMC)  17 . The transfer may also be made via a private ethernet  43  through respective service processors  40  and  41 , respectively, servicing systems  10  and  11  and coordinated by HMC  17 . However, the key to this mobile transfer is that both source system  10  and destination system  11  must be able to access, through their respective virtual server partitions  15  and  16 , an external storage system: the SAN  19  that is supported by a storage system  20 . 
     The present invention, which will be described with respect to  FIG. 2 , provides for an alternative LPAR transfer implementation for situations wherein either or both of the source and destination systems cannot access the external storage, i.e. SAN  19 . When a transfer of the mobile partition is initiated, as described with respect to  FIG. 1 , and it is determined that either of the source  10  or destination  11  servers cannot access storage area network SAN  19 , a routine  49  is initiated via hypervisor  14 , in destination server system  11 ,  FIG. 2 , wherein the destination server accesses via a path  46 , illustrated by a dashed line, the storage  44  supporting mobile partition  12 . After first determining that there is local storage at the destination server capable of storing a mirror image  45  of storage  44 , the destination server  11  accesses the storage supporting partition  12  via path  46  through connecting network  18  and source server hypervisor  13  using iSCSI protocols wherein the virtual disk storage  44  supporting mobile partition  12 , controlled by VIOS server partition  15 , is treated as a target device. A mirror image of disk storage  44  is created and transmitted back via path  46  through connecting network  18  and destination server hypervisor  14  using iSCSI protocols wherein the mirror image of disk storage  44  supporting mobile partition  12 , controlled by VIOS server partition  15 , is now stored in local storage  45  of destination server system  11  and is now available to support mobile partition  12  that can now be transmitted via connecting network  18  using iSCSI protocols. 
     Accordingly, mobile partition  12  is now fully transferred and functional on destination server system  11 , as if it were transferred as in  FIG. 1 . 
     With respect to  FIG. 3 , there is shown an illustrative diagrammatic view of a control processor that may be used for power hypervisor  13  and  14  of  FIGS. 1 and 2 . A central processing unit (CPU)  31 , such as one of the microprocessors or workstations, e.g. System p™ series, eServerp5, eServer OpenPower™ or the PowerVM Standard edition, available from IBM, is provided and interconnected to various other components by system bus  21 . An operating system (OS) 29 (e.g. a Linux System) runs on CPU  31 , provides control and is used to coordinate the function of the various components of  FIG. 2 . Operating system  29  may be one of the commercially available operating systems. Application programs  30 , controlled by the system, are moved into and out of the main memory Random Access Memory (RAM)  28 . These programming applications may be used to implement functions of the present invention. ROM  27  includes the Basic Input/Output System (BIOS) that controls the basic computer functions of the hypervisor. RAM  28 , storage adapter  25  and communications adapter  23  are also interconnected to system bus  21 . Storage adapter  25  communicates with the disk storage device  26  of the server system. Communications adapter  23  interconnects bus  21  with the ethernet network. I/O devices are also connected to system bus  21  via user interface adapter  34 . Keyboard  32  and mouse  38 , when appropriate, may be connected to bus  21  through user interface adapter  34 . Display buffer  22  supports an appropriate display  33 . 
       FIG. 3  is a general flowchart of a program set up to implement the present invention for providing an alternative implementation for moving a mobile LPAR from a source server controlled system to a destination server controlled system in a virtual processor system environment wherein the system is divided into LPARs, step  70 . 
     Provision is made for the system determining if both the source and destination server systems involved in an initiated partition move have access to the same SAN, step  71 . 
     If the determination is made that both the source and destination systems have access to the SAN, then provision is made, step  72 , for: 1) transmitting the mobile LPAR over a connecting network from the source to the destination server systems through iSCSI protocols, and 2) transmitting all data storage supporting the mobile LPAR via the SAN. 
     On the other hand, if the determination is made that either server system or both do not have such access to the SAN, then, step  73 , provision is made for: 3) creating a mirror image in the source server system of all data storage supporting the mobile LPAR; 4) transmitting this mirror image over a network using iSCSI protocols to local storage associated with the destination system; and 5) also transmitting the mobile LPAR over a connecting network from the source to the destination server systems through iSCSI protocols. 
     As mentioned hereinabove with respect to the description of  FIG. 2 , a routine is provided via the hypervisor  14 , in destination server system  11 ,  FIG. 2 , wherein the destination server accesses the storage supporting mobile partition. This routine will now be described with respect to  FIG. 4 . Upon a determination, step  81 , that either or both the source and destination server systems do not have access to the SAN, provision is made for confirming that local storage associated with the destination server has storage capability for the mirror image of all data storage supporting the LPAR being transferred, step  82 . Upon such confirmation, provision is made for the creation of a mirror image of all data storage supporting the LPAR by the destination server treating the LPAR data storage at the source server system as the target device of the destination server from which the mirror image is created, step  83 , and then transmitted over a network using iSCSI protocols to the destination server system at which the data storage supporting the transferred LPAR will be stored on the local storage associated with the destination system, step  84 . 
     A simple illustrative example of a run of the process set up in  FIGS. 4 and 5  will be described with respect to the flowchart of  FIG. 6 . The system awaits the initiation of a mobile LPAR transfer, step  90 . If Yes, a transfer has been initiated, a determination is made, step  91 , as to whether both the source and destination server systems have access to a SAN. If Yes, then, step  92 , the LPAR is transmitted via the connecting network and the data storage supporting the LPAR is transmitted via the SAN. Upon completion of the transfer, the flow is returned to step  90 . 
     If the determination in step  91  is No, both servers do not have access to SAN, then, step  93 , a determination is made as to whether local storage capability can be located at the destination server system for storage of the LPAR supporting data storage. If No, storage cannot be found, then, step  94 , a failure message is sent. However, if Yes, local storage is available, then, step  95 , the destination server treats the data storage for the LPAR at the source system as a target device and creates a mirror image of the data storage for the LPAR, step  96 . The mirror image is transmitted via a network using iSCSI protocols to the destination server, step  97 , and the LPAR is transmitted via the connecting network from the source server system to the destination server system, step  98 . The storage data supporting the transferred LPAR is stored in the local storage at the destination server wherein the storage is available for the transferred LPAR, step  99 . At this point, a determination may conveniently be made, step  100 , as to whether the transfer session is at an end. If Yes, the session is exited. If No, the process is returned to step  90 . 
     While the primary implementation of the present invention offers the above-described alternative solution to LPAR transfer systems wherein source and/or destination server systems do not have access to a SAN, there is a further application to some exisitng LPAR transfer systems in which both the source and destination server systems do have access to types of Fibre Channel SANs that have a very limited range of connectability. By way of background, Fibre Channel (FC) is a network technology used to a great extent for storage networks. It is an industry standard technology provided by the International Committee for Information Technology Standards (INCITS) of the American National Standards Institute (ANSI). FC has become a standard connection for server systems having limited ranges of connectability, e.g. systems in the same building or in a limited area facility. In such FC systems, a need may arise for storage transfer over longer distances. In such situations, the alternative implementation of the present invention may be considered as an alternative to the Fibre Channel SAN. In this connection, it should be noted that Fibre Channel Protocol (FCP) uses SCSI commands for its transmissions. 
     Although certain preferred embodiments have been shown and described, it will be understood that many changes and modifications may be made therein without departing from the scope and intent of the appended claims.