Storage vMotion simultaneous disk copy

[eborovac]

Hi,

Does anyone have information on the following VMX parameter?

svmotion.maxSimultaneousDiskCopy

According to VMWorld 2019 presentation it's supposed to enable simultaneous disk copy during storage vMotion.

However, my testing shows that after applying advanced parameter storage vMotion still copies only one disk at a time.

Any ideas will be appreciated.

Thanks.

[ssetty]

Storage vMotion can perform up to four simultaneous disk copies per Storage vMotion operation. This advanced vmx parameter can be used to change this default behavior. However, we only let one active disk copy per datastore pair, regardless of the vmx option. Typically, S/XvMotion network throughput is limited by the storage IO bandwidth either on the source or destination datastore. Hence, if there is an active disk copy for a given datastore pair, we do not schedule a new one.

[mctom]

In other words, if the disks are all on the same data store such as vSAN in a HCI environment.  It only migrates one disk at a time.  We also found that we had to add the svmotion.maxSimultaneousDiskCopy=1 parameter to the advanced settings of the VM that contains large disks (over 1TB) or a svmotion from cluster to cluster would be incredibly slow and would often fail at the final switchover point.  A 12TB VM failed at 28 hours before the change and it completed less than 8 hours after the change.