External Hard Drive Size for Backup

What kind of backup? A pure clone of your data (SuperDuper style), which gives you an exact copy of whatever's on your drive, or a versioned backup (Time Machine style), which keeps old versions of files, as well as files which get deleted (deliberately or not) from your system drive? The latter will inevitably take up more space. How much "stuff" do you have on your drive at the moment, and by how much do you expect to expand in the foreseeable future?

If your total used space is 300MB or less, and you don't expect to increase it too much anytime soon, a 1TB backup drive will be fine for Time Machine. If you plan to load up with a lot of large files (eg video), you need to look at other solutions.


Matt

As an aside, you should consider at least two external backup drives, with one being stored securely in a different physical location. Just in case.

I always get a drive that is larger than my internal one, and I have a 1TB drive for Time Machine, it uses an enormous amount of space, particularly since I back up my Entourage data. A 1 TB drive is probably the smallest you should get for your internal drive, you never know when you might want to put a bigger drive in.

DP's suggestion of two drives is good, I have one that I use SuperSuper! to clone, and another for TimeMachine. I really should have a third one off site, but don't feel any pressure to do it, although I should.

I ALWAYS build my own drive (takes 5 mins). More storage and less money.


I like the TD-M120 enclosure, it's the best I know of.

Has a cooling fan, shock absorbers, and all the ports you will ever need.





http://www.cooldrives.com/ox93saiihadr.html


http://www.onnto.com.tw/product.asp?sys_sysno=31

And this drive:



http://www.amazon.com/Western-Digital-Intellipower-Desktop-WD20EADS/dp/B001RB1TI S/ref=sr11?ie=UTF8&s=electronics&qid=1258862242&sr=8-1


I presume you don't use three because you've never suffered through a flood or fire that destroyed everything in the house.

THAT will cause a person to use three drives

A business should always have three with one stored securely off site.

DP, if there were a fire in my house, the first thing I would do would be to grab my cloned external drive, the second would be to call the fire department 😉

DP, I don't keep an offsite drive (yet) either, but you are making a really good case for me to start doing it. It's something we all don't like to think about but disasters can and do happen. I guess we need to spread our eggs out so that some will survive!

Regards,
Steve M.

Message was edited by: Steve M.

Yup. It used to be that the first thing someone would grab in a fire is the photo album. Considering that our lives are mainly digital these days it really wouldn't take much to make it all go away.

Indeed. And then there is the aspect of some of our various digital formats we use now going "extinct." I'm still fascinated by that article called "Digital Ice Age" that was in Popular Mechanics a few years ago.

There's also that aspect of someone doing online backups and then waking up one day and finding out that the online company has vanished.

Regards,
Steve M.

I'm pretty much in agreement with the others here.

I have an iMac, so there's no likelihood I'll ever upgrade its 1TB internal drive. My previous Mac also was an iMac; it had a 320 GB (or 300 GB, depending on whether you choose the decimal or binary nomenclature) internal drive, which I just about filled up over the 2 years I had it, so that's the amount of data I currently have on this machine. Obviously, I have gobs of free space available on my current internal drive.

I always back up my internal drive via Time Machine (incremental), as well as SuperDuper! (clone). So I keep 2 externals on hand for that. My personal "rule of thumb" has been (and continues to be) to have an external Time Machine drive 1.5-to-2.0 times the size of the volume (total amount of data) I anticipate having on my internal drive. Inasmuch as that covers a lot of estimating over a multiyear time horizon, it leaves a lot of room for "error." Since I'm currently operating with about 320 (decimal) GB of data (including system files) on a 1 (decimal) TB internal drive, and I don't anticipate any exponential growth in my saved data over the next few years, I'm quite comfortable using a 1 TB external drive for my TM backups now, and migrating to a 1.5-to-2.0 TB external drive later if and when the need arises, which likely would be accompanied by improved storage technology and lower storage costs.

As far as SuperDuper! is concerned, it only needs an amount of room equal to the internal volume's size (again, not the drive, but the volume—i.e., totality of data), plus some additional "head room" for "working space" to do its backup. My personal rule of thumb for this has always been 10-to-15%. So for now (and likely for some time to come), all I need is a 500 GB external drive (smaller, actually...but they don't make a standard size drive larger than 320 GB but smaller than 500 GB) for my SD! clone. Again, when my needs change, I'll consider a larger drive.

Hope this helps.