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HMC V8 R8.7.0 SP1 Enhancements

By HARIGANESH MURALIDHARAN posted Mon June 08, 2020 07:27 AM


Typically HMC does not add new functional enhancements in a service pack, but we want to rapidly deliver enhancements you need or have requested and don't want you wait for the next major release that would force an upgrade to get new functional enhancements. Hence the following functional enhancements have been added to HMC V8 R8.7.0 SP1, along with other general and security fixes.

Live Partition Mobility (LPM) Performance Improvement:

When a partition is activated, the hypervisor maintains a structure named the Hardware Page Table (HPT) which is a translation table from a partition's effective/virtual addresses to the physical location of the memory.  The size of the table can be set on a partition basis but defaults to 1/64 of the maximum memory for an IBM i partition or 1/128 the maximum memory for a AIX, Linux or VIOS partition.  The size of the HPT controls the number of entries that are available to map from the partition's address space to the physical hardware.  When an LPM operation is started, the hypervisor switches from the default Hardware Page Table to a secondary Hardware Page Table referred to as the Physical Page Table (PPT).  The PPT provides the same translations from partition address space to physical address space but the PowerVM hypervisor is able to manage the PPT in a manner that allows the hypervisor to track pages that have changed during an LPM operation.  To provide a coherent view of the partition's memory, any changes that are made to memory when the partition is on the source server must be transmitted to the target server.  


By default the PPT is smaller than the HPT to reduce the overall amount of memory required by the hypervisor with the belief that LPM is usually performed during lower periods of activity for the partition.  As LPM has grown in popularity and with the addition of some very memory intensive application like SAP HANA's in-memory database, some of the original assumptions about LPM are no longer correct.  To address this changing environment, HMC level 870 SP 1 (V8 R8.7.0 SP1), PowerVC 1.4.0 and FW860.40 have added support for a profile attribute that allows the PPT size to be specified on a partition basis similar to the existing HPT ratio value.  The default value for the PPT ratio for AIX, Linux or VIOS is 1:8192 which minimizes the allocation of memory.  In lab experiments, running SAP HANA benchmarks, it was determined that the 1:8192 ratio was not providing enough page table entries and the performance of the SAP HANA application was degraded during LPM.  We changed the partition PPT ratio size to 1:2048 to allow for more page table entries during migration.  This resulted in a small difference in the SAP HANA application performance when LPM was actively migrating as compared to times when there were no LPM operations in progress.  To set the PPT ratio, specify the ppt_ratio parameter for the partition profile you want to change using the chsyscfg HMC CLI command or if you are creating a new partition/profile, you can use the mksyscfg command.Valid values are 1:64, 1:128, 1:256, 1:512, 1:1024, 1:2048 and 1:4096.  Note that a ratio of 1:64 will require 64 times the firmware memory than a ratio of 1:4096.  Also, since this is a partition profile option, the partition must be powered off and activated with the updated partition profile attribute for the hypervisor to allocate a different size PPT.  Note, a larger PPT will not improve the overall time to migrate a partition, it just reduces any application slowdown while LPM is active.  


In summary, if you are currently satisfied with the application performance when LPM is active, there is no need to set the PPT ratio but if you are performing LPM during active times and the application performance is less that desired, the PPT ratio is available to reduce the impact of LPM. If you are using PowerVC, you can set the PPT ratio in the compute template with PowerVC 1.4.0

Net Promoter Score:

Enhancement has been added to collect On-premise Net Promoter Score (NPS) for Power Systems. See What, why and more about Net Promoter Score for details on NPS. Each user will get a pop-up survey for the systems they can access, based on the system type. The initial pop-up will be after 30 days and once every 180 days from then on.

UI Enhancements:

While we keep adding new features and continuously work on performance improvements,  we are always looking for constructive feedback on the Enhanced UI. You can post your questions on Discussions in HMC Topic or the IBM PowerVM LinkedIn group.

IBM i IO Hosting Network Support (RFE 100278):

While the HMC V8 R8.7.0 release added support for creating & managing IBM i hosted virtual SCSI adapters, per customer request, HMC V8 R8.7.0 SP1 adds support for creating & managing IBM i Hosted Virtual Ethernet Trunk Adapters.


Delete Partition Enhancement:

The delete partition GUI has been enhanced to provide a new option to delete the associated Virtual IO Server mappings when deleting the partition. Choosing the option would delete all the Virtual IO Server mappings (vSCSI, vFC, vNIC) and the server adapters associated with the partition. The option would need an active RMC connection to the Virtual IO Server partition hosting IO for the partition getting deleted. Using this option would avoid having stale server adapters on the Virtual IO Server after a partition is deleted.


 Virtual Network Enhancement:

Logical Partition Virtual Network Management has been enhanced to add multiple virtual Ethernet adapters with same Virtual LAN & Virtual Switch to a partition.

Performance and Capacity Monitoring (RFE 106608):  

Based on customer request, Performance & Capacity Monitoring REST API’s has been enhanced to collect metrics on Physical Processor Pool. 

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