We have 650 GB of high-availability SAN space at our data center. We just received a bill for "overage" on our SAN space usage, which was odd, because we've never had more than 650 GB of data on the drive.
After much back and forth, we've determined that they implemented a proprietary monitor which records writes to the SAN space, and have started billing for overage when you exceed 650 GB of disk WRITES rather than 650 GB of data at rest, which is how they've handled things before.
They offered no warning about the change, and gave us no advanced notice. They have no tools, no apps in their portal, and no reporting system to notify us when we are close to exceeding our monthly usage total.
I've used apps before which monitor if a disk is full, but I've never needed a tool that monitors total writes to a hard disk.
Does such a tool exist?