Large incrementals on *file* backups
I've seen lots of discussion of this, but I've seen so many contradictory answers, I guess I'll ask again and hope someone with actual knowledge of product internals will shed some light.
I have two *file* backups set up, both as incrementals. Each is about 100G in size for the full backup. One is pretty consistent in size, typically 500M or so. The other varies hugely. I'll get several incrementals of 2-4G, then suddenly I'll get a incremental of 40G.
I understand how on *disk* backup a defrag of the disk will impact the size, since a *disk* backup is a sector-by-sector copy. But presumably a *file* backup is a file-by-file copy which shouldn't be affected by location on the disk and thus shouldn't be impacted by a defrag.
Win 7 Pro/64 bit
TI 13 Build 5551
I can only imagine that your backup is somehow include files unintentionally (like the volume information, or some index, or some NTFS junction). Try to unhide files in Windows, then launch ATI and verify your file selection.
Of course anything is possible, but I doubt this is the explanation. First off, I always run with hidden files displayed, so it's not like there should be a surprise there. Second, barring the odd chance of some program generating a junction, I don't use them (other than the fact the backup is D:/users which is linked to c:/users by a junction. (C: is my SSD and I didn't want to use the space for user data.). There is no other user of the machine, so it's not like someone else might be moving a lot of data that I don't know about. And last, perhaps most telling, if I do a full backup immediately after the incremental, it's roughly the same size as the original full backup, so the only way it could have an incremental of almost 50% of the size of the original is if files accounting for 50% of the space changed (and they didn't, since a huge part of this is my photo archive which is completely static).