Optimizing restore operations
To help optimize virtual machine (VM) restore operations, adjust the settings for the vmmaxrestoresessions, vmmaxrestoreparallelvms, and vmmaxrestoreparalleldisks options. With these options, you can optimize restore operations while balancing the resources on the Hyper-V hosts.
Overview of the restore options
The following information provides an overview of the vmmaxrestoresessions, vmmaxrestoreparallelvms, and vmmaxrestoreparalleldisks options and factors to consider when you are configuring these options for performance.
You might also want to complete restore operations for a limited number of VMs by using the default values and then increase the values if you want to decrease the restore time for the remaining VMs.
In general, increasing the option value results in improved network throughput. However, at a certain point, increasing this value will no longer increase performance. For example, if a 1 GB network is used, when the network is saturated, the throughput will not increase if the option value is increased. In addition, the increased values might result in a higher CPU utilization that negatively affects resource availability on the host.
If network and processor resources are shared with other operations, higher option values might also adversely affect performance on those operations. For example, if the network that is used for restore operations is also used for regular network traffic by the VMs, the VMs might experience slower network speeds during restore operations.
If your priority is to improve throughput, increase the default values. If your priority is to minimize impact to the hosts, decrease the values.
- vmmaxrestoresessions
- The vmmaxrestoresessions option is used to control the maximum number of
IBM Spectrum Protect server sessions that can be used in an
optimized restore operation at one time. Although this option sets the maximum number of sessions
that are allowed, the data mover that is running on the Hyper-V host and network speeds determine
the actual number of sessions that are required based on the incoming workload.
For maximum performance, the minimum value of the vmmaxrestoresessions option must be equal to or greater than the value of the vmmaxrestoreparalleldisks option multiplied by the value of the vmmaxparallelvms option. If the value of the vmmaxrestoresessions option is below this minimum value, it will be increased at runtime to the appropriate value.
You might have to experiment to find the optimum value for the vmmaxrestoresessions option. Each dispatched VM is guaranteed one session and then extra sessions are applied to the dispatched VMs. The number of sessions will not exceed the value that is specified by the vmmaxrestoresessions option.
The benefit of increasing the vmmaxrestoresessions option value is limited if your storage system performance is slower than the available network speed between the data mover and the server.
For example, increasing the value of the vmmaxrestoresessions option can make better use of the network and disk resources on the systems, though you might have to reduce the number of restore sessions to ensure that the network transfer and disk speeds are not at capacity. If you must use a higher number of restore sessions, consider adding more disks or splitting the VMs across different storage pools or storage devices on the Hyper-V host.
- vmmaxrestoreparallelvms
- The vmmaxrestoreparallelvms option is used to control the maximum number of VMs
that can be restored at any one time. The optimal value for vmmaxrestoreparallelvms
depends on the processing power of the Hyper-V host and the performance of I/O between the host and
the IBM Spectrum Protect server.
For example, if you are moving data from the server over a busy or slow LAN, you might have to limit the number of VMs in each parallel restore operation.
Similarly, if the Hyper-V host processing capabilities are limited for any reason, you might also want to limit the number of VMs.
To help optimize performance, use a minimum of a 10GB network in your Data Protection for Microsoft Hyper-V environment.
- vmmaxrestoreparalleldisks
- The vmmaxrestoreparalleldisks option is used to control the maximum number of virtual disks that can be restored at the same time per VM, regardless of the value of the vmmaxrestoreparallelvms option or the number of VMs to be restored. If sufficient sessions are available as specified by the vmmaxrestoresessions option, the data mover will restore the number of virtual disks per VM at a time as specified by the vmmaxrestoreparalleldisks option.