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TheRealPeterP
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troubleshooting cold migration performance

Hello folks,

I am struggling with speed (or lack thereof) of cold migration.

Host1 -> Host2 migration returns horrible speeds over 1Gbps link (like 3, 5, maybe 10 Mbps).

Host 2 -> Host1 migration fully utilises 1Gbps link.

The reason I am using cold migrations is that a) there are different CPU architectures on Host1 and Host2 b) I ain't got vMotion license.

Running iperf between the hosts showed no issues, either direction was >940 Mbps, vmkping worked with zero issues as well with sub 0.5ms response times either way.

Creating dedicated vmkernels with only 'provisioning' ticked on both hosts made no difference.

Host1 uses spinning disks, Host2 SSDs. Host2 -> Host1 migration runs at full speed, so writing to spinning disks is not an issue.

What caught my eye is that during the slow migration, performance overview shows roughly 40k-70k network packets sent per second, however the traffic remains horribly slow (down to single, maybe low double-digit Mbps, as outlined above). When doing the migration in the 'fast' direction, the packet numbers per second are maybe 3-6x higher, but the actual traffic is 150-200x higher. MTUs across the environment are at 1500.

The VM size I am trying to transfer is nearly 1TB, so waiting for it to transfer at 5Mbps speed is not an option 😃

Any ideas, which log may contain useful data? Which tools might be of help? Where else to look? Happy to provide any information.

All suggestions, nudges, links will be appreciated!

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