vMotion multi-threading and other tuning settings

When you need to boost overall vMotion throughput, you can leverage Multi-NIC vMotion. This is good when you have multiple NICs so it is kind of scale-out solution. But what if you have 40 Gb NICs and you would like to do scale-up and leverage the huge NIC bandwidth (40 Gb) for vMotion?

vMotion is by default using a single thread (aka stream), therefore it does not have enough CPU performance to transfer more than 10 Gb of network traffic. If you really want to use higher NIC bandwidth, the only way is to increase the number of threads pushing the data through the NIC. This is where advanced setting Migrate.VMotionStreamHelpers comes in to play.

I have been informed about these advanced settings by one VMware customer who saw it on some VMworld presentation. I did not find anything in VMware documentation, therefore these settings are undocumented and you should use it with special care.

Advanced System Settings	Default	Tunning	Desc
Migrate.VMotionStreamHelpers	0	8	Number of helpers to allocate for VMotion streams
Net.NetNetqTxPackKpps	300	600	Max TX queue load (in thousand packet per second) to allow packing on the corresponding RX queue
Net.NetNetqTxUnpackKpps	600	1200	Threshold (in thousand packet per second) for TX queue load to trigger unpacking of the corresponding RX queue
Net.MaxNetifTxQueueLen	2000	10000	Maximum length of the Tx queue for the physical NICs