This read-only Counter64 reports the number of files, or inodes, in this jail, with the source description noting that a value of zero means the count is unknown. An admin monitors this to detect a jail accumulating an excessive number of small files, which can exhaust inode limits on the underlying filesystem even when raw disk space usage looks normal. As an illustrative example, jailDiskFiles climbing into the hundreds of thousands on a jail running a mail queue could indicate stuck or undelivered messages piling up as individual files.