Investigation would show that, the first configured/saved policy was identified as the cause of the disk full error, as it had thousands of policy versions saved. We saw that the "maximum number of policy revisions to store" was set to 1700.
From Administration > Settings > General, it's possible to control just how much policy revisions to store in /data directory on the disk, on the MC.
Each time you edit or import a policy, a revision of the policy is stored. By default, Management Center keeps an unlimited number. However, this can result in storage issues so you are able to specify the number of revisions of policy to store before Management Center begins to prune. You can specify up to 9999 revisions. Please, refer to page 475 in the MC admin. guide with URL below.
We recommended to have this setting significantly reduced, to help MC begin to prune the already saved policies, to better manage the storage space.
As an immediate fix, to create the desired space in the /data directory, we recommend to have the relevant policy, beginning from the older ones, exported and saved, externally, having already, successfully, pushed the policy to the target appliances, and then you may delete the policy from the MC. In doing this, it should be noted that the exported policy should be tested, by importing the same, to ensure it's health, before any deletion of the same is done. For guidance on how the saved policy may be exported/imported/deleted, please refer to the snippet below.