PowerVM

Live Partition Mobility (LPM) Improvements in PowerVM 2.2.5

By Pete Heyrman posted Tue June 09, 2020 09:08 AM

  

 

PowerVM 2.2.5 LPM Logo

PowerVM Version 2.2.5 is a major upgrade that includes many new enhancements.   As with prior PowerVM releases, one of the major areas of focus has been improvements to Live Partition Mobility (LPM).  LPM is at the heart of any cloud solution and provides higher availability for planned outages.

LPM Resiliency and Performance

Most customers utilize a dual VIOS configuration to ensure the highest level of availability of client partitions.  With PowerVM version 2.2.5 we are leveraging this configuration to provide additional resiliency and performance.  Prior to version 2.2.5, there is a single Mover Server Partition pair that is responsible for the transmission of the data from the source server to the target server even in a dual VIOS configuration.  The Mover Server Partition (MSP) is the term used to designate the VIOS that is chosen to transmitting the partition’s memory contents between servers.  With the upgrade to PowerVM 2.2.5, changes have been made to utilize two MSPs in a dual VIOS environment. 

PowerVM Dual MSPs

 

Utilizing multiple MSPs will provide additional resiliency in the event that an individual MSP fails, a connection fails between an MSP pair or for any assortment of other issues.  If an MSP connection were to fail, PowerVM will seamlessly continue the migration on the remaining MSP pair.  In addition to better resiliency, most migration operations will see reductions in the time to perform the migration operation.  The support available in version 2.2.5 is designed to transmit the memory contents from the source to the target simultaneously over both pairs of MSP connections.  In concept, half the data would be transmitted over one of the MSP connections and the other half would be transmitted over the second MSP connection.  For large memory partition, the transfer of the memory contents is what consumes the bulk of the LPM time.  So, for large partitions, you could start to approach a 50% decrease in the time to perform LPM operations with version 2.2.5.  Of course, the network infrastructure would need to be able to handle this additional load to see a performance improvement.  Another point is that the MSPs perform best if both MSPs have the same network bandwidth (the current LPM recommendation is to utilize dedicated 10Gb network connections in each VIOS). Even if the network connections are different speeds between the MSPs, there will still be a resiliency benefit and some performance benefit.

 

With PowerVM 2.2.5, the default for migrations from the HMC user interface and the HMC command line interface (migrlpar command) is to enable this enhanced support automatically.  Net, if you are utilizing a dual VIOS configuration, by default you will see the additional benefits just by upgraded to PowerVM 2.2.5.  In addition, if you are utilizing the HMC command line interface, on the migrlpar command you can specify the - -redundentmsps parameter to override the default behavior.  A value of 0 for this parameter indicates that the migration should be done without the additional redundancy and performance benefit (similar to the behavior prior to version 2.2.5).  A value of 1 indicates that redundant MSPs is required and the migration will not be successful unless there are two MSP pairs available for the migration.  This would be useful if you require the additional resiliency.  A value of 2 (default if nothing is specified) indicates that redundant MSPs are desired.  Net, PowerVM will try to use two MSPs but if only one is available, the migration could be successful even on a single MSP pair between the source and target servers.  In addition to specifying the behavior, you also can specify the MSPs and the network interfaces that should be chosen through the use of the source_msps and target_msps parameter on the migrlpar command.  Use the following link to find out more information about redundant MSPs.

Option to specify Fiber Channel Port versus disk level (LUN) and FC Port level validation on individual migration operations

PowerVM Version 2.2.4 allows you to select the level of NPIV storage validation that best fits your environment.  This specification is set on a VIOS basis by setting the src_lun_val and dest_lun_val attribute on the LPM pseudo-device (vioslpm0).

 
Starting with PowerVM version 2.2.5, the migrlpar command allows the choice between port only versus disk and port validation for migration validation operations.  The "--npivval" parameter on the migrlpar command supports values of port to select only port level validation and portdisk to select disk plus port level validation.  The value specified for the "--npivval" parameter will override the default VIOS setting for this migration validation operation.

Contacting the PowerVM Team

Have questions for the PowerVM team or want to learn more?  Follow our discussion group on LinkedIn IBM PowerVM or IBM Community Discussions


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