"mount changed" message

[sdsl]

I noticed a message in a few SuperDuper logs recently. It says "mount changed" for a disk, but as you can see below from the log excerpts I have included, neither the source nor target disks were the disk whose mount change was being reported. Any idea what the meaning of this might be? The clone seems to have completed successfully.

| 10:00:51 PM | Info | Source Volume: Photo Disk 1 Clone, mount: /Volumes/Photo Disk 1 Clone, device: /dev/disk2s2, media: WD My Passport 083A, interconnect: External USB, file system: "Journaled HFS+", OS: N/A, capacity: 2000.02 GB, used: 1665.87 GB, directories: 166488, files: 640987, ejectable: YES, ACLs: Enabled
| 10:00:51 PM | Info | Target Volume: photos-3TB, mount: /Volumes/photos-3TB, device: /dev/disk1s2, media: WD My Passport 0827, interconnect: External USB, file system: "Journaled HFS+", OS: N/A, capacity: 3000.11 GB, used: 14.26 GB, directories: 109, files: 982, ejectable: YES, ACLs: Enabled
... [many lines in log]
| 03:54:20 AM | Info | Disk disk0s3 mount changed!
| 03:54:21 AM | Info | Disk disk0s3 mount changed!
... [many lines in log]
| 12:36:51 PM | Info | Evaluated 807472 items occupying 1665.02 GB (166487 directories, 640943 files, 42 symlinks)
| 12:36:51 PM | Info | Copied 807022 items totaling 1664.89 GB (166466 directories, 640514 files, 42 symlinks)
| 12:36:51 PM | Info | Cloned 1665.02 GB of data in 52530 seconds at an effective transfer rate of 31.70 MB/s

[sdsl]

P.S. After checking a bit more, it seems that disk0s3 is the recovery disk partition (hidden). I suspect that this message does not involve SuperDuper, but it did get reported through SuperDuper's log, and I've never seen that message anywhere else. Maybe every so often the recovery partition gets quickly mounted and then unmounted as some kind of check by the operating system?

[dnanian]

We log all drive mount operations in case they *are* relevant. They're not errors.