HyperV UB Fails to start could not initialize memory there is not enough space on the disk

SUMMARY

could not initialize memory there is not enough space on the disk (0x80070070)‎

ISSUE

When attempting to start Unitrends Backup on HyperV the guest fails to start 

Hyper-V reports: Could not initialize memory there is not enough space on the disk (0x80070070)‎

RESOLUTION

Increase the volume size of the host or remove other data from the volume to provide sufficient space for Hyper-V to create BIN files used to cache guest memory operations.  

As a workaround you could reduce the memory used by Unitrends Backup or other guests, however this may have a negative impact on performance and should only be done under the advisement of Unitrends support.

We suggest 1vCPU and 4Gb of RAM per concurrent task. [Each concurrently running backup job, Hot Copy Job, Cold Copy job plus 1 task for background processing if using Incremental Forever.] Please see UB Deployment Best Practices for more information.  If UB resources are reduced, be cautious when reducing RAM as reducing RAM size dramatically, removing so much RAM as to result in available RAM being below prior database memory allocation (a portion of physical RAM), the Unitrends database may fail to start.  When reducing CPU count, also reducing concurrent backup limits may be required.  See How to change the number of concurrent backups

ADDITIONAL NOTE:  NTFS volumes should always be configured to have sufficient free space minimums.  15% for volumes 1TB and smaller, 10% for 1-5TB volumes, and 5% for volumes over 5TB.  Failing to maintain sufficient free space could result in NTFS corruption.  On systems with production VMs that will be snapshot, additional space for avdx files needs to be considered as well. If you are actively monitoring and reporting free space, 15-30% free space is usually sufficient, however, if free space monitoring is not being used, Microsoft recommends instead free space equal to the sum of the VHD/VHDX files on the volume that will concurrently have snapshots as a failsafe to handle worst case scenarios where snapshots may fail consolidation and grow to the original VM size.  Such use is rare to encounter but within possibility.  

CAUSE

In order for a VM to be started on hyper-V, Microsoft requires allocated space equal to the following formula: Cumulative sum of VHD/VHDX and AVHD/AVHDX files, PLUS space for BIN files (equal to the total RAM allocated to running guests). Note while guests are stopped, BIN files are not present, they are only present while a guest is powered on. 

For example, if you have a 100GB thick provisioned VM without snapshots, it will take approx 100GB on disk when powered off.  If that VM is allocated 16GB of RAM, an additional 16GB of disk will be consumed while the guest is powered on for a total of 116GB used disk.  If there is insufficient storage to accommodate this additional space Hyper-V will prevent the guest from booting.  Add an additional 15% to this number to ensure minimum safe NTFS free space, plus additional free space if snapshots will reside in these volumes.  

Consider guests may use dynamic memory configurations which may make these calculations difficult, however, total concurrent guest memory use cannot exceed physical host memory.  


 

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