vSAN1

Hi!

Does anyone know, if the vSAN rebalancing process has limitations in smaller environments? I have started the process manually multiple times. In the first run, the process reduced the imbalanced data significant, but the cluster warning still exist. After a second run, i have noticed, that the imbalanced data was unchanged. And so on.

How is your experience with the rebalancing process in vSAN?

I had similar problems and think there are some issues with how this works (at least with VSAN 6.2), which has been raised as a bug and will hopefully be addressed in future releases. It's discussed in a previous post on this community:

Rebalance Virtual SAN Cluster task stuck at 5%

Thanks

Per

Doing rebalancing from vSphere web client works but is not optimal. Progress shown isn't a real indication (will just show 5%), default rebalance will balance disks within 30% of each other. Because the health check also checks for 30% variance, once one of the high/low variance disks is different by 1%, it can cause the health check to show a rebalance warning again.

Instead I would recommend using RVC to perform and monitor a rebalance VSAN 6.0 Part 9 - Proactive Re-balance - CormacHogan.com :

vsan.proactive_rebalance -s -v 0.10 -t <num of seconds to spend rebalancing> -i 300 -r 200000 <cluster num>

and use vsan.resync_dashboard <cluster num> to monitor the status

The above uses a variance of 10% (-v 0.10) instead of default 30%. Because the health check is checking for 30% variance, this should be better since you will be left with only 10% variance after rebalancing. The -r is the rate of resync change allowed (in MB per hour) per host.

A little update: "Virtual SAN Disk Balance" warning alarm during vSAN health check (2148484) | VMware KB