I have three 1TB drives in a software RAID-5 configuration with LVM running on top of it. Each drive is partitioned into 2 500GB partitions. So as far as mdadm knows, it has 6 devices.
Currently the raid array has 2.5TB of space; I'm assuming one of the 500GB partitions is being used for parity? Or maybe 500GB is being used throughout the array, I'm not exactly sure.
My question is: with this configuration, am I safe if any one of the drives fail? Or, do I need to add a fourth drive with another 500GB partition as a spare? Or do I need to add another 500GB partition from a fourth drive and somehow specify it to be used for parity?