Hello,
I have a question relating to the amount of free space to leave on a datastore. I recently upgraded to vCenter and with that came along some datastore usage alarm definitions. I see they were set to 75% and 85% as it relates to warning and error thresholds. This got me to thinking, how much should I really be leaving free on my datastore's. I realize this may be subjective given you can't always predict growth needs for a guest VM nor can you predict memory requirements. My philosophy to this point has been to us up as much as I can as to not "waste" knowing I can simply migrate the VM to a new LUN should the need arise to either expand a vdisk or allocate more memory. I'm willing to accept any risk that I wouldn't have time to do a cold migration to a new LUN should the need arise, I simply don't see any situations where I wouldn't be able to accommodate a cold migration to a datastore with sufficient free space.
So my question: am I flawed in my thinking? Am I missing something that could come back to bite me if I simply fill up my datastore's to make the best use of them? Is there a best practice for free space (I'm assuming the 75% and 85% thresholds aren't a best practice, simply a guideline well more like a arbitrary number VMWare threw in w/o much thought behind it). What are others leaving for free space?
Any assistance anyone could provide would be greatly appreciated!
Blake Frericks