Mirror Sync randomly turns into FULL sync for no reason

[GWA]

Hello,

I back up a PC every night with 2 external USB drives. I have the sync set to Mirror as I only need the updated changes made on the PC to back up. This works 99.99% of the time without problems.

I have just done another Sync with the same two USB drives. The first Mirrored the PC changes, only 60 files or so and Synced in about 30 seconds.

The second USB drive said it was 47,000 files to Sync and would be 2h:30mins.

I can see no reason for this to happen?

Both USB back up drives are only used for this back up, none of them have been used since the last mirrored backup on Friday. It is only a one way process - PC to USB only.

Does anyone else have this issue? This is not the first time this has happened either.

Any info appreciated.
Gary.

[TAC109]

Sometimes problems like this are caused by a change to Daylight Saving Time. Click the link for more information.

[GWA]

Thanks TAC109,

I have just checked and that seems to be the issue. The problem USB drive is FAT32 while the one that was OK is NTFS.

Much appreciated.