Analytics data drive free space is less than 15% > Vcops will initiate removal of data

Hi,

I'm new to vCOps, so please bear with me.

We have vCOps running in a test setup for about half a year now. Recently it's been giving these administrative alerts on the Analytics VM:

"Storage drive (/data) free space is less than 15%. vCenter Operations Manager will initiate removal of data to reclaim disk space. To avoid automatic data removal, add an additional disk."

I was looking into this, but I cannot figure out what data is being removed or how vCOps chooses data to be removed.
For example, the metric history of the Analytics VM goes back only 3 weeks, some hosts metric history goes back to beginning of august. Other hosts metric history go back to beginning of September.

So I guess vCOps has been clearing data to reclaim disk space, but...

Is there some logic on what data is being removed?

Is there any documentation on this?

We have 110 hosts and around 1250 VM's. What's the recommended size of the /data storage drive?

thanks in advance.