The ping column tests the response time of the disk by measuring how long it takes to read 1 MB, it does so every second.
Additionally, it tests for dropped out connections. If you check "ping" a handle is open to the disk, if after this time the disk disconnects, even for a short period, the pinging will stop and the ping column will turn red indicating that the disk has dropped out in the past.
So it serves a few functions:
- To test for disk drops.
- To visually identify a disk by the disk access light, which will light up once every second.
- To see the disk response time (albeit, this is not its main purpose).