How many time machine backups should you keep?

Time Machine should be backed up to a separate drive from the startup drive. I assume you are doing that. Time Machine will fill the space and automatically delete the earliest backup as needed. So, you really don't have to worry about that.

Pondi has a site that gives great information on it. I'm sure someone will post it. If not, I will look for it later and post it here.

Message was edited by: Glenn Leblanc ** Here it is: http://Pondini.org/OSX/Home.html Great information

I keep 1 TimeMachine and 1 CarbonCopyClone.

TimeMachine saves individual files, so the system can be backed up while active.

CarbonCopyClone (or SuperDuper, both equally effective) make bit-by-bit clones of the drive, and these clones are bootable in case of disaster. And you can re-clone it back onto a new drive in case you need to change the internal drive. But also the system needs to be more-or-less "idle" to get a full clean image.

I have two drives, both self-powered, both external.

It sounds like you have other data on your TM drive, in the same partition, besides the backups. That's not a good idea -- see #3 in Time Machine - Frequently Asked Questions.

It sounds like you've been doing this for a while, and the external is (or has been) fairly full. If so, you probably can't make a very large new partition now, without erasing the old one, but it's possible. See #3 in Using Disk Utility.

If not, you'll have to manage the backups manually. 😟 Once you get a new drive, try to either dedicate one whole drive to your backups, or at least make a separate partition for them.

And by the way, since you have an iMac, there's no reason not to leave the TM drive connected, and let it back up the changes hourly. You'll be protected much better that way.

TM only copies files that changed. If you change few fles, then each hourly backup will be very small. And backups are rolled off based on remaining space on the TM drive, so several small hourly backups is the same as 1 large weekly backup.

But several hourly backups have a better chance of saving that *one particular* file you need because it is always watching.

TM keeps hourly backups on the current day. Yesterdays backup will be consilidated to a daily backup up to a month back. They then get consilidated to weekly backups.

So, you're not having hundred of backup weekly. You will only have 4 per month.

Your TM drive should be at least as big as your main drive depending on how much of it is being used. Since I'm using about only 1/10 of my main drive space, my TM drive is same size as my main drive. After a year, my TM drive uses twice the space of my main drive, so I still have a very long way to go before it full and starts deleting.

If you store a lot of data and you're using a good portion of your main drive, then you should double the capacity of your TM drive compared to your main drive.

When is it enough backup? Depends on what you're doing and how important your data is to you. If your computer is for play, then it may not be that important to you. But if you keep valuable information that you don't want to loose, then you want to make sure you have a good backup plan which includes multiple sources. I've actually found myself looking a year back to find something and was very glad to have it in TM.

Since my main HD is large enought for me to be using less than 25%, my external drive is twice the size. I partitioned it into 2 volumes so I could use TM on 1 volume and I have a cloned backup to the other which gets updated weekly. That way, if my internal drive fails, I can boot into the external.

EU4 wrote:

Thanks Pondini. I had this drive only dedicated to backups, but until I can buy another drive in a few weeks, I had to move some other things on there to make space on my internal drive.

In that case, if the drive wasn't near full yet, you may still be able to make a small, temporary partition for the "other" stuff, per #3 in Using Disk Utility. If so, copy the other files there and delete them from the TM partition, and let Time Machine "do it's thing."

When you get the new drive, format it for a Mac, per #1 in the same link. Copy the "other" stuff there, then you can delete the temporary partition and expand the TM partition back to fill the drive again, per #4 there. Then remove the new drive from the exclusion list so Time Machine will back it up along with your internal HD, per #10 in Time Machine - Frequently Asked Questions.

You kind of answered my question, but I'm still confused. You said there's no reason not to have the TM drive connected and let it back up hourly. But if you do this everyday, you'll have hundreds of backups in a week. So my original question stands, when is it enough to back up?

As the others have posted, it will take some additional space, but not a great deal, since it "thins" them down to one per day for a month, then one per week, and each backup only copies what's different from the previous one.

And if it starts erasing old ones and you don't want it to, isn't that bad? Thanks!

That's not bad, unless you've deleted things from your system, relying on Time Machine to keep the backup copies indefinitely. If you've been doing that, see #20 in Time Machine - Frequently Asked Questions.

Otherwise, no, it's not a problem, because although TM only backs-up what's new or changed, every backup is, in effect, a full backup, so it always has backups of everything on your system. See #12 in the FAQ for details.