backing up a laptop and a iMac

I would maybe raid the disks together or get another just to be safe.

I think you need to clarify what you want to do.

Do you want to backup the existing startup drives of each machine, or just select data to clear space?

In honesty potentially worth doing both.

Do you want a bootable external drive/drives with a copy of the existing installation/s?

Do you simply want to store an image of teh startup drives which could be reinstalled to the internal or external drive for startup purposes?

For simple backups you could certainly use Time Machine, preferably using separate drives/partitions for each Mac. You'd be best starting from a new empty/newly partitioned drive, though you can also store data alongside Time Machine data.

As much as Time Machine is theoretically simple to use, I personally prefer to manually backup either to bootable clones or large disk images (you could store several on an external) which could be restored to a bootable drive if needed. You might want to look at Carbon Copy Cloner or SuperDuper demos to see if they'd suit you.

Remember that if your wife clears space on one Mac, then any 'backup' is not really that as the data will have been moved to an external and unless you have other copies is vulnerable in case of the external failing. Many would advocate keeping several backups, and a backup offsite in case of fire/theft.

Ultimately it all boils down to what data is truly important and needs to be backed up and available for posterity - certain emails, documents, family photos/video would be the most important for most. Media like iTunes video, CD rips etc may be 'valuable' but for the most part could be replaced (or redownloaded from the cloud in teh case of most iTunes purchases - though not guaranteed forever).

In essence I think you need to clarify what exactly you are trying to achieve.

Forget software RAID with external drives. It will more than likely bite you.

Also for automatic backups you might want to consider Apple's Time Capsule.

Additionally, keep in mind that you should always maintain an absolute minimum 10 - 15 GB of empty space on your hard drive (I'm referring to your almost full hard drive on your laptop). So, no matter what backup you choose, you most likely need to delete some stuff.

My 2 cents:

Your plan of partitioning the 2Tb external drive(s) and using it to back up should be fine.

You might want to consider using software such as Carbon Copy Cloner to make the backups - it will make a bootable backup if the hardware allows it:

https://www.bombich.com/

and then starting a proactive regimen of cloning the computers on a routine basis. Once the first clone is done, Carbon Copy Cloner will only transfer any changes made to the primary disk to the backup - so these backup sessions take much less time after the initial clone.

There are other cloning apps out there, but I have personal experience with Carbon Copy Cloner so am suggesting that. Others may have different recommendations.

Also, any backup plan is improved by redundancy - making two physical clones of your computer drive, and stashing one in a safe place - will increase the chances of recovery should a problem strike.

And . . . you need to check your backups periodically to verify that they themselves are viable as well.

The most important thing, no matter what method you use, is to get back ups of your drives immediately.

MtD

has55 wrote:

I have a laptop Mac Pro 13" , mid 2009 and iMac 20", mid 2007 . the iMac is running 10.10.3. the laptop is running 10.7.5 and is almost full for its 250 GB. The iMac only has used about 70GB out of 250 GB. I have two WD 2 TB external hard rive. I was thinking of partitioning both drive into two partitions. I was going to used one drive for the iMac putting a bootable back on one partition and use time machine on the other partition. I'm not sure what do with the laptop since it's almost full. My wife said she will remove some items, but honestly I think it will still be near full. Does anyone have any suggestions and the method I'm describing for the iMac ok?

Has55,

It's basically a very poor idea to use 1 single EHD as a backup for TM and a bootable clone. the reason is simple. When the EHD dies (and they all do) you will have lost all of your backup. It is wise to have 2 backup schemes for each computer however NEVER use the same EHD for both, eventually it will come back and bite you when you least expect it! I also recommend getting each machine it's own EHD and buying higher quality drives such as OWC (www.macsales.com) Mercury Elite Pro series. You will find many experienced users on these forums will agree with me.

Alley_Cat wrote:

Also for automatic backups you might want to consider Apple's Time Capsule.

A Time Capsule, or alternately an Airport Extreme Base Station with a drive attached to its USB port, is an excellent "no hassle" way to keep an up-to-date backup of a Mac laptop using Time Machine, because whenever the laptop is in range of its WiFi network it will do hourly backups or transfer the latest local backups to it. The first backup will take quite a while to complete but after that, since only new or changed items will be added it should work fairly quickly.

But as others have said, ideally you should have multiple backups of everything, at least for any items you can't afford to lose, & they should be on different drives.

R C-R wrote:

But as others have said, ideally you should have multiple backups of everything, at least for any items you can't afford to lose, & they should be on different drives.

And, if living in Texas or Oklahoma, in different houses or higher ground….

. Does this sound ok?

Not really, my recommendation is clear. Each computer should have 2 EHD's connected to it, one EHD for Time Machine and the second for a bootable clone using either SuperDuper or Carbon Copy Cloner.

You can partition the external drives; I have 3 of them and I have two up-to-date copies of each of the systems I am running (Mavericks and Yosemite) plus one each of the systems factory fresh (for reinstalls/emergencies/selling it) plus other partitions for extra backups of my all important folders/photos, etc. They are spread around: current Mav clones on EHD 1 + 3, Yosemite 1 + 2, factory fresh 2 + 3, etc, etc. My externals are only 1 TB as I prefer to have more drives rather than fewer very large ones as I don't have tons of GB in videos or photos.

As for your laptop: having the hard drive full is bad - regardless of your backup strategy, you need to delete some space hogging files there permanently. You should an absolute minimum of 10 - 15 GB empty space at all times, more is much better.