In my Macbook Pro, I have two internal drives and I've connected a third drive via USB in enclosure.
I am currently doing a secure wipe of the external drive and I was interested in seeing what the disk I/O was for that particular drive, but when I use Activity Monitor I only see the total disk usage for all drives combined.
Is there any way to monitor a specific drive's total I/O, preferably via a built-in or free method? I don't want to filter by process ID. I just want to filter by mounted disk.
EDIT: It seems like for normal mounted drives, the Terminal program
iostat should be sufficient. However, for unmounted drives (like ones which are being secure wiped in Disk Utility) iostat will not show the drive even though Activity Monitor seems to have a way to report the disk I/O for it.