Enabling Replication Reduces VM Write Speeds

Question

We want to use Hyper-V Replica to copy VMs to a DR site (connected via 10GB fiber). I have found that VM write speeds to VHDXs (small and large) are drastically reduced. I'm attaching an image of benchmark testing. This is the behavior I'm seeing in the VM, not the host.

This behavior has been seen on all VMs with a variety replication partners.

Here's an example of the configuration.

VM: Windows Server 2016 Standard | Gen 2 | 8->32 GB RAM | 12 CPU | SCSI Controller

Hyper-V Environments:

• Windows Server 2019 Standard | 382 GB RAM | DA two tier storage (SSD->HDD)
• Windows Server 2016 Datacenter Cluster | 383 GB RAM | CSV on Equallogic via 10GB private network
• Windows Server 2019 Datacenter Cluster | 447 GB RAM | CSV on StorageCenter via 40GB private network

Is Replica the appropriate tool for disaster recovery? If not for the performance, it seems that it should be ideal.

Answer 1

Hi,

After some research, I didn't find any known issue that Storage Replica makes VM VHD write speed slow. In that case, I suspect if there's any issue with the storage replica or cluster storage. Since it's hard to troubleshoot performance issues on forum, I would suggest you open a case with MS to do deep troubleshooting.

Below is the link to open a case with MS:

https://support.microsoft.com/en-us/gp/customer-service-phone-numbers

Known issue with storage replica listed below, for your reference:

https://learn.microsoft.com/en-us/windows-server/storage/storage-replica/storage-replica-known-issue[customer-service-phone-numbers][2]

Thanks for your time!
Best Regards,
Anne

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