[SOLVED] Time Machine asks to reuse backup on every backup.

Hey guys, I've ben living with this problem for… well as long as I can remember, and it's finally time to fix it.

I have two computers using one Time Machine Disk. The physical disk is connected to my Mac Mini, and it's shared over the network to my MacBook Air. The picture below is the backup disk in case you didn't guess. The notebook is my MacBook Air:
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So the MacBook Air backs up just fine, but every time my Mac Mini tries to back up, it pops up with "Would you like to reuse the backup "*DIRECTORY TO MACBOOK AIR'S BACKUP*" with this computer?" also shown in the picture below. So I click "Create new backup" and it seems to backup in the Mac Mini's backup folder like it should… until next time.
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I just want it to back up normally, both of them, without asking me anything first. Until now, I've just disabled automatic backups for my Mac Mini and would backup whenever I felt needed.

 

Do you mean partitions? How would I tell it to back up to a specific folder?

Oh yeah, sorry about that. I've edited my OP. I do click the "Create new backup" button though, and sadly, it still asks.

 

So I just had an idea. Maybe it won't do this if I backup my MacBook Air first, and then backup my MacMini. This would involve me deleting and re-backing up my MacMini though, so I just wanted an opinion on if this might work or not.

 

Okay, so that didn't work. Please, anybody. I have no idea what to do.

 

Yeah, I thought about that. It would work, so I guess I'm not completely stuck, but the drive is already partitioned for Backups and Storage, so it's getting messy. If all else fails I will end up going down that rout. Thanks for the reply.

Right now I'm trying to get it to backup to a specific sparse bundle. I'm also kind of following this guide to see if it fixes this.

 

Fixed it. I will write instructions here just in case I or anyone else has this problem again.

I fixed it by getting Time Machine to back up into a sparse bundle rather than a regular folder. I also think I know why/when Time Machine uses a sparse bundle rather than a folder: it only uses them over a networked drive so it has something to mount(?).

Step 1) So here is how I did it. I duplicated "Josh's Notebook.sparsebundle" and then mounted it.
Step 2) Then I option clicked the little backup menu bar icon, and selected "Browse Other Time Machine Disks" and selected ""Josh's Notebook" on "Time Machine Backups""
Step 3) Then click the little gear button and select "delete backup" for every backup. (This was to save room)
Step 4) I went to "/Volumes/Time\ Machine\ Backups/Backups.backupdb/Josh's\ Notebook" and I deleted it.
Step 5) I had a few problems emptying the trash because of error 8003, but I don't know if you will. Just to be safe, I ran "sudo rm -rf /Volumes/Time\ Machine \Backups/.Trashes" But if that doesn't work, you have to do all this "chflgs" stuff and whatnot. I don't know how to do it.
Step 6) I renamed "Josh's Notebook copy.sparsebundle" to "Josh's Desktop.sparsebundle".
Step 7) When Time Machine said it had found Josh's Desktop.sparsebundle to backup in, I clicked "Reuse this Backup"

So it does mount a drive every hour, but at least it doesn't ask me anything.
Thanks for the help everyone.