What happens to a backup file if it is defragmented?

"There is no point in defragmenting the backup file, since restoring the backup is not something that one does all day long.

In any case, there's much less reason to defragment an external drive than an internal one.

So my advice is to ignore Windows on this point and leave this drive alone."

"External drive has Mac files on it saved for 7 years. All was well until yesterday I introduced another Mac save trying to place a disk image upon the external backup device, and the disk image was too large, so think perhaps some files were moved or scattered as you described great above. Neither of my 2 Macs (G4 powerbook 17"" Mac laptop from 2004 with 1.5GHz processor, and iMac G5 desktop all-in-one screen 1.83Ghz) can read the backup device and its icon doesn't appear on the desktop when plugged in. Same with disk utility not recogizing this suddenly. Then I tried putting the USB into the Dell PC 3GHz (2006) desktop, and it recognized the Mac files to my surprise. I'm now thinking of doing a defrag, so is this ok. Just trying to get things back to normal so my macs can save data back upon the external HD made by western digital (200GB from about 2006 or so). Thought once you have formatted an external backup drive with apple files then that's it and a PC can't do any saves. This is older tech keep in mind now backup drives have dual capability. My device does say ""Combo"", so maybe I'm in luck? Can the PC resave from this device and back out the other usb port and into a new memory device (like a 500GB new drive that I will run to the store and buy today?), and will it be able to be read as they were saved originally by the 2 Macs?

Why the Macs won't read is either because I had to pull the plug during a disk image save, and/or things got fragmented as per the discussion above... trying not to panic but this is 8yrs and 25000 hours of research on it (too tired from 24/7 attempts to cry)"

If performance is not the issue, defragmentation is not neccesarily bad. It just means that the file is not all in one place, but scattered around the disk.