If you ever tried to do any file operation via the management interface of an ESXi host, like uploading an ISO file or running a backup using Network Mode, you may know the management interface is not running at the full speed of the underlying network interface, and the bandwidth you end up using is only a percentage of the total available. This limit is designed to preserve the availability of the management interface, but still there are situations where this limit is a problem, and you would like to increase it. Hopefully, there’s a solution.
My test environment
In order to check first the performance of my management interface, I set up first a quick backup with Veeam Backup & Replication v9. I configured my backup proxy to forcedly use Network Mode:
Then, I created a quick backup to save a single virtual machine with this proxy; since Network Mode is slow, I chose a small VM: DC02 is one of my domain controllers and its size is 40GB (34,3GB used). Also, all the tests needs to be run manually as Active Full backups, in order to skip CBT optimizations and be able to compare results. Also, the backup repository for this test runs as a virtual machine over a Fusion-IO flash card, in order to be sure that the target is not the bottleneck of the job and so I can truly compare the results. The first run gave me this result:
Network Mode tuning via NFC settings
Following the KB from VMware Poor performance while deploying virtual machines over the network, there are two settings that can be changed to improve performance, buffers and flush interval. These values can be changed using Tech Support Mode, and can influence the performance of the NFC channel.
To increase the number of buffers from 2048 to 4096, run this command:
# esxcfg-advcfg -s 32768 /BufferCache/MaxCapacity
To reduce the Buffer Cache Flush interval from 30 seconds to 20 seconds, run this command:
# esxcfg-advcfg -s 20000 /BufferCache/FlushInterval
Note: You can apply these settings if you are running at least ESXi 5.0 Update 2, and you need to apply them to all the involved ESXi servers.
After changing these settings, I’ve tried to run the backup again:
As you can see from the numbers, speed increased from 57 to 74 MB/s, a 30% improvement in performance. I’m not going to claim that in any condition the increase is going to be 30%, but nonetheless the increase is pretty significant. This can be a really quick and effective way to speed up backups using network mode, both in 1GB and 10 GB environments.