Here’s a nice little tip which has helped my ESX production deployment no end. By default ESX 3.5 will only vmotion 2 guests at a time which if you have a few on the host can add up a bit of time. It can also cause update manager to fail if the vmotion of the guests takes too long.
Simply change the vpdx.cfg file (normally in c:docs & settingsall usersapp datavmwarevmware virtualcenter ) file on your vcenter server to the value you desire and restart the virtualcenter service.
The change is required inbetween the <vpdx></vpdx> marker tags and you will need to insert the following:
<ResourceManager>
<MaxCostPerHost>16</MaxCostPerHost>
</ResourceManager>
Now the trick with this is to decide what you want the max cost to be and as usual there is a little light maths involved:
A Hot Migration = 4
A Cold Migration = 1
So if you wanted 4 hot migrations to run concurrently then you would need to add 16 as the max cost. As with all fiddling with production servers you should make a backup of the vpdx.cfg file first before making any changes and then make small changes to the max cost ensuring nothing is honking during the migrations.
