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What good is Time Machine if you can't span disks?

krye

krye

macrumors 68000
Original poster
I have a 750G drive as my boot drive. I have not yet picked up a descent Time Machine drive yet so I just threw a spare 320 in there to hold me. Time Machine worked great and I could go back several months. All was well and good until the other day.

My main drive has now reached about 320 gigs. So my Time Machine backup is pretty much a 1-to-1 copy. So I can only go back about a day. This is not good.

Now is the time to buy a bigger drive. Here lies the problem. If I go for another 750, eventually I will run into the 1-to-1 copy problem. If I buy a 1TB drive then OK, but eventually when my 750 fills up, the 1TB isn't going to be much good since it will probably only give me a few days worth of backups. The rule of thumb was supposed to be that your Time Machine drive be at least twice the size as the drive it is backing up. (Don't know if that's an Apple thing, or just something the community agreed on. Probably the latter.)

It would be nice to have a 750G drive as my main drive and 2x1TB of Time Machine backup space. But Time Machine does not let you span drives. So what are you supposed to use if you have a 1TB hard drive that is full? Time Machine becomes kind of useless if it's a 1-to-1 copy. The whole point is that you can go back in time and retrieve a lost file. So ideally, keeping at least 1 month would be nice. I mean, how long is it before you realized you lost something?

Anyone have any tips, tricks, or RAID solutions? Comments?
 
krye said:
I have a 750G drive as my boot drive. I have not yet picked up a descent Time Machine drive yet so I just threw a spare 320 in there to hold me. Time Machine worked great and I could go back several months. All was well and good until the other day.

My main drive has now reached about 320 gigs. So my Time Machine backup is pretty much a 1-to-1 copy. So I can only go back about a day. This is not good.

Now is the time to buy a bigger drive. Here lies the problem. If I go for another 750, eventually I will run into the 1-to-1 copy problem. If I buy a 1TB drive then OK, but eventually when my 750 fills up, the 1TB isn't going to be much good since it will probably only give me a few days worth of backups. The rule of thumb was supposed to be that your Time Machine drive be at least twice the size as the drive it is backing up. (Don't know if that's an Apple thing, or just something the community agreed on. Probably the latter.)

It would be nice to have a 750G drive as my main drive and 2x1TB of Time Machine backup space. But Time Machine does not let you span drives. So what are you supposed to use if you have a 1TB hard drive that is full? Time Machine becomes kind of useless if it's a 1-to-1 copy. The whole point is that you can go back in time and retrieve a lost file. So ideally, keeping at least 1 month would be nice. I mean, how long is it before you realized you lost something?

Anyone have any tips, tricks, or RAID solutions? Comments?
Click to expand...

i'm a bit confused. 1 to 1 copy? when it reaches the limit of what the hard drive can hold, it deletes the oldest files to replace the new ones. so if your 320 held a good several months, it will keep holding several months worth of data. a TB would probably hold a year worth of data, and once it reaches the limit, it will delete the oldest files to put in the newest.

i might have misread something here but please inform me if i did
 
Get a case that holds 2 drives and you can put 2 750s or 1TB drives in it, jumpered in a raid that TM will see as 1 drive of 1.5 or 2TB
 
FuuFuu said:
i'm a bit confused. 1 to 1 copy? when it reaches the limit of what the hard drive can hold, it deletes the oldest files to replace the new ones. so if your 320 held a good several months, it will keep holding several months worth of data. a TB would probably hold a year worth of data, and once it reaches the limit, it will delete the oldest files to put in the newest.

i might have misread something here but please inform me if i did
Click to expand...

My boot drive is 750 Gigs and has 320 gigs on it. My Time Machine drive is 320. So it can't hold anything more than 1 copy. Once I go over 320 gigs, the Time Machine drive won't even be able to make a 1-to-1 copy.

So what I'm asking is what are you supposed to use for Time Machine when you have a 750G or 1TB drive that is full? The 1.5TB drives just came out, and are way too expensive. Wouldn't a Time Machine made of 4x500GB be great? So can you make a RAID and use it for Time Machine?
 
roland.g said:
Get a case that holds 2 drives and you can put 2 750s or 1TB drives in it, jumpered in a raid that TM will see as 1 drive of 1.5 or 2TB
Click to expand...

roland.g is absolutely correct. Your best option here is a RAID array of some sort. Your expansion options are virtually unlimited if you go this route. 😉
 
roland.g said:
Get a case that holds 2 drives and you can put 2 750s or 1TB drives in it, jumpered in a raid that TM will see as 1 drive of 1.5 or 2TB
Click to expand...

Can this be set up in a Mac Pro or do you have to use an external?
 
To try and make this a bit clearer....

You have a single 750GB drive holding your OS, Apps, and user data. You had been using Time Machine to backup to a 320GB drive.

You're now using ~320GB of your 750GB drive which means that all your backup will hold is one copy, the latest, of each file. Pretty much rendering it the worst "Time Machine" ever.

So, you could...

Get 2x750GB/1TB, and RAID them up as a single volume using software RAID in Disk Utility.
Get a NAS with RAID and lots of big disks.
Get a RAID external drive cage (eSATA maybe) with lots of big disks.
Completely rethink your backup strategy. Do you really need to go back in time? Isn't just having a single backup good enough?
 
krye said:
Can this be set up in a Mac Pro or do you have to use an external?
Click to expand...

If I understand your original post, you have two internal drives currently, which means that you should have room for two more. If this is true, you can purchase two additional drives and put them in your MacPro and RAID them together using Disk Utility. You do not have to use external drives, but they are an option. 😉
 
Tallest Skil said:
Why are you having it rebackup EVERYTHING every day?! Your system files, applications, fonts, and the like don't change daily.
Click to expand...

TM doesn't re-backup daily. It doesn't keep 2x your drive size for 2 days. It creates a single backup, and then incremental backups of changes only, every few hours and then every day replacing the hourly ones. TM is fairly smart in it's self-management on that account.
 
edesignuk said:
You have a single 750GB drive holding your OS, Apps, and user data. You had been using Time Machine to backup to a 320GB drive.
Click to expand...

I get it now.

Just back up YOUR files. If anything goes wrong, just reinstall from the disk and then put your stuff back on.
 
Zyniker said:
If I understand your original post, you have two internal drives currently, which means that you should have room for two more. If this is true, you can purchase two additional drives and put them in your MacPro and RAID them together using Disk Utility. You do not have to use external drives, but they are an option. 😉
Click to expand...

edesignuk said:
To try and make this a bit clearer....

You have a single 750GB drive holding your OS, Apps, and user data. You had been using Time Machine to backup to a 320GB drive.

You're now using ~320GB of your 750GB drive which means that all your backup will hold is one copy, the latest, of each file. Pretty much rendering it the worst "Time Machine" ever.

So, you could...

Get 2x750GB/1TB, and RAID them up as a single volume using software RAID in Disk Utility.
Get a NAS with RAID and lots of big disks.
Get a RAID external drive cage (eSATA maybe) with lots of big disks.
Completely rethink your backup strategy. Do you really need to go back in time? Isn't just having a single backup good enough?
Click to expand...

FuuFuu said:
what he said
Click to expand...

Perfect guys! This is exactly what I needed to hear. I didn't realize that software RAID could be done from within disk utility. I think that would sold my problem.
 
krye said:
Perfect guys! This is exactly what I needed to hear. I didn't realize that software RAID could be done from within disk utility. I think that would sold my problem.
Click to expand...

yep, it works great. I have 3x500gb drives in my mac pro in a 1.5tb raid0 stripe, and 2x750gb in raid0 in an external esata enclosure for my time machine backups.
 
Buy a drobo and have 2.7 TB of Time Machine space?

You can of course build your own RAID of larger capacity for less money. But drobo seems to be a robust machine that eliminates the work on your part.

It seems that Time Machine may not be especially well suited for the 750GB data cases. You're getting into a netherworld of backup difficulty. Can you archive some of the data that isn't accessed regularly and / or have Time Machine exclude certain very large data sets that don't change frequently and don't need rolling backups?

Perhaps two RAIDs: one for Time Machine to capture dynamic data and one for less frequent archive captures (e.g. with a SuperDuper! type program).

Good luck! You've got a tough and somewhat pricey backup challenge.
 
What about this:

Bay 1 .......... Bay 2 .......... Bay3
320G .......... 320G ............ 750G
......... RAID0 ............... Time Machine

That gives me 640G in a fast RAID as my boot drive, and 750G for Time Machine.

Since I already have the 750G and the 320G, all I have to do is drop in another 320 for a lousy $73 bucks. And I'll have an open bay for future upgrades.

Does this sound good?
 
You could adjust Time Machine to replace only items that change.
I have mine set to only back up My Documents Directory.
 
bigrell486 said:
You could adjust Time Machine to replace only items that change.
I have mine set to only back up My Documents Directory.
Click to expand...

I'd like to be able to do a complete system reinstall from Time Machine should my boot drive give up the ghost.
 
krye said:
I'd like to be able to do a complete system reinstall from Time Machine should my boot drive give up the ghost.
Click to expand...

One recommendation in regards to Parallels or VMware Fusion (if you use it) is to set TM to NOT backup the virtual machines folder. TM backs this up everyday whether you use it or not and it backs up the entire virtual machine rather than the changes. For example if you have 10GB allocated for Windows XP TM will backup the whole 10GB everyday which wastes drive space.

Two things you can do, one is to drag and drop your virtual machines folder onto your external drive like a NAS or just allow TM to perform one backup and then add it to the list NOT to backup any further.
 
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