Tag Archives: esxi commandline

vCenter 5.5 web interface and the Cubic congestion algorithm

It has been a while since I last posted, but thought this one might be of interest to a few of you, especially since I keep running into it every so often.

Some time ago I did a performance analysis of multiple manufacturer NICs. As a part of that test, I also tested the impact of changing the TCP congestion algorithm in VMware from the default New Reno to Cubic. The cubic algorithm consistently delivered better throughput results in the tests, and since then I have updated all of our hosts to use this.

Unfortunately, if the algorithm is set via the VMware 5.5 vCenter Web Interface, not all of the required changes are applied properly to the target ESXi host and upon reboot, the host is unable to connect to vCenter. It took quite a bit of work with VMware until we discovered the root cause. Fortunately, we did identify a simple workaround, documented here:  https://communities.vmware.com/thread/506836   Continue reading

Manually disable vmreplica state (unable to extend disk)

Just ran into an issue with a VMware VM that was at one time replicated offsite using VMware’s replication tool. For some reason, when the service was decomissioned, (at least) one of our VMs was still marked as a replicated machine. When a VM is marked as active, then it will not be possible to extend the disk drive. In our case it appears that it was also in the middle of a replication, long since abandoned.

To fix, we found this article: StuffThatMightBeUseful

In the article, the author points out that the VM needs to be shut down. Probably better if the VM is down, but in our case we did not have this option and changed the setting on the running VM. Worked and did not crash. yet.

The steps are simple:

  1. Find the VM_ID (number in 1st column): vim-cmd vmsvc/getallvms |grep “name of your VM”
  2. Confirm current state: vim-cmd hbrsvc/vmreplica.getState VM_ID
  3. Fix: vim-cmd hbrsvc/vmreplica.disable VM_ID