I am trying to get a good understanding of why out of the box the value within Unity Cx disk capacity is set to 95%? Is it recommended to leave this setting alone and mitigate using msg aging and mailbox size? Or has someone found a better value to set this at? Reason I ask if the disk capacity reached 95% you are near to issues...why not set this lower to give you more advanced warning?
You can definitely adjust this setting to give you more advanced time to take action before Unity Connection disk space is exhausted. However, when the hard disk fills to the specified percentage limit set on The Disk Capacity page (System Settings > Advanced > Disk Capacity page in Cisco Unity Connection Administration), the Connection conversation changes, and Connection users are no longer allowed to send voice messages to other Connection users. Connection also logs an error, which can be viewed on the Tools > SysLog Viewer page in the Real-Time Monitoring Tool. So if you have the limit set at 80%, even though you have 20% capacity remaining (which is more the rule of thumb I've worked with for disk space), your UC users cannot send voice messages to other UC users. I have left my limit at 95% and routinely check/monitor the server as well as implement message aging.