Time Machine Disk Backup Size

I just ordered a 1 Tbyte external hard drive that I want to use for Time Machine backup. My internal iMac hard drive is 1 Tbyte. I only have about 100 Gbytes on the iMac right now, but I am a little worried about not having ordered a larger backup drive, because since I ordered it, I've read recommendations of 2X or 3X for the backup drive. I have not seen a minimum requirement for this on the Apple website.

Will I eventually run into problems because the external drive is not larger than my internal drive? If my internal drive volume approaches being full, will I still be able to restore from Time Machine backup disk of the same size, to at least one or two backup dates?

I understand that, as my hard drive fills up, there will be fewer and fewer backup dates available on the Time Machine backup disk, but I don't have a sense as to how much of a problem this is if the boot disk size = the Time Machine backup disk.


thanks! Kevin

Don't worry about it for now. Since you only have around 100 GB on the drive, you still have plenty of time and room before Time Machine starts deleting old backups.

Remember, the first backup you make with TM is a full backup. Each one after that is incremental. And you can adjust how often you wish to backup with third party software or by removing the drive and attaching it only when you want to backup.

chscag said:

Don't worry about it for now. Since you only have around 100 GB on the drive, you still have plenty of time and room before Time Machine starts deleting old backups.

Remember, the first backup you make with TM is a full backup. Each one after that is incremental. And you can adjust how often you wish to backup with third party software or by removing the drive and attaching it only when you want to backup.

Click to expand...

@chscag - hope you don't mind if i but in your conversation but i'd like to ask something about what you said that caught my attention... I've already raised some questions regarding Time Machine Backup before but no one mentioned about this to me. They just said that old back will be automatically deleted once my back up drive is full. So just to enlighten me more does what you said mean that the first back up won't be erased just in case my Time Machine backup drive is full? sorry for the intrusion but your help clarifying this would mean a lot. thanks!!!

What Time Machine will do is erase the oldest backup to make room. You should always have a full backup available to restore from. Each subsequent backup after the initial is an incremental, however, Time Machine is smart enough to keep things in order.

I just went through that myself. My oldest backup was erased by TM after it warned me that it was going to do so to make room. But when I opened TM and explored, I still had a full backup, only it didn't go back in time as far as it did before.

Make sense?

chscag said:

What Time Machine will do is erase the oldest backup to make room. You should always have a full backup available to restore from. Each subsequent backup after the initial is an incremental, however, Time Machine is smart enough to keep things in order.

I just went through that myself. My oldest backup was erased by TM after it warned me that it was going to do so to make room. But when I opened TM and explored, I still had a full backup, only it didn't go back in time as far as it did before.

Make sense?

Click to expand...

thanks for clearing it up! sorry for the my naiveness on this matter. still new to macs well at least i learn something new everyday with your guys around! hope you guys won't get tired answering my pesky questions. thanks!!!

This is all very informative for me, too, soon I'll have a 1TB drive to use for TM. I know almost nothing about TM, so I'm really glad to see what's being said about it here.