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EricSandvik-7151 avatar image
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EricSandvik-7151 asked ·

Enabling Replication Reduces VM Write Speeds

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.

37468-writespeedimpact.jpg


windows-server-hyper-v
writespeedimpact.jpg (467.7 KiB)
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EricSandvik-7151 avatar image EricSandvik-7151 ·

Also found that if the VM has multiple VHDXs, and replica is configured to only replicate some of them; hrl files are still created and used for all drives.
This means that slow write speeds are encountered on volumes that are not being replicated.

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XiaoweiHe-MSFT avatar image
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XiaoweiHe-MSFT answered ·

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://docs.microsoft.com/en-us/windows-server/storage/storage-replica/storage-replica-known-issuecustomer-service-phone-numbers

Thanks for your time!
Best Regards,
Anne

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EricSandvik-7151 avatar image EricSandvik-7151 ·

My question is in regards Hyper-V Replica, not Storage Replica.

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XiaoweiHe-MSFT avatar image XiaoweiHe-MSFT EricSandvik-7151 ·

Hi,

Since there's little information about the issue on the Internet, and as far as I know, to troubleshoot the performance issue, it's required to collect performance logs and storport logs and other related logs for deep analysis, since log analysis is out of forum support, it's recommended to open a case with MS for better help, thanks for your understanding!

Best Regards,
Anne

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