This INTEGER reports the percentage of free space on the specific disk identified by multiDiskIndex, mirroring diskPercent but per drive. Because different disks on the same appliance can fill at very different rates (e.g., a busy log disk versus a static OS disk), this per-disk percentage is what should actually drive low-space alerting rather than a blended system average that could mask one nearly-full disk. An alert threshold set on this specific value for the log disk, rather than an aggregate, would catch the problem before it causes a logging outage.