I'm using a 13-inch 2013 macbook air with 4gb memory, and after a near disaster with a spilt drink I've realised I need to start backing it up. I don't know what size external hard drive I need though, as I don't want to spend lots of money on something if it's not entirely necessary. Any suggestions?

  1. Choose a reputable manufacturer: As data shows, HGST (formerly Hitachi, now owned by Western Digital) makes the most reliable hard-drives on the market today. Stay away from Seagate drives (see comments).
  2. Choose the right size drive: Regardless of the method, it's highly recommended to purchase an external drive that is atleast twice the capacity of the internal drive it’s backing up.
  3. Use Time Machine: There is no better local backup method for OS X. Alternatives exist in the form of archives (cloning your drive to another), but this is not a true, continuous backup.

Sidenote: Networked backups using Apple’s Time Capsule is a reliable, wireless, way that is equally viable and definitely more convenient. The obvious con of this solution is the price-tag.

Assuming your internal drive is no bigger than 500GB, here is the drive I would recommend: HGST Touro 1 TB 5400-RPM USB 3.0 External Hard Drive.


  • I own four HGST Touro drives. All have operated extremely well with no mechanical issues or problems to date. This is only my personal experience - which is all the more reason why it’s important to note that the Touro is the top-rated external hard drive on Amazon according to average customer reviews.
  • @bmike brought up an important point. The Backblaze study on HDD failure rates used enterprise grade drives of 3.5’’ form factor. The consumer grade 2.5’’ external HDD’s, those relevant to the original question, were not the subject of these tests. See the comments below.
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    What HGST drive would you recommend for home backup use? I have had great results with seagate for desktop backups and seagate and WD for portable backups and Time Machine. I'm wondering if the 2.5 inch drives have different reliability characteristics than back blaze which runs the drives in a data center and has them always on. – bmike May 9 '15 at 15:47
  • @bmike yes, that’s a good point you make. Those tests were run on 3.5’' enterprise grade drives. I’d recommend either the above HGST drive (for the size of the OP’s backup), or Toshiba’s 2TB Canvio. I’ve had awful experiences with Seagate’s 3.5’’ drives (x2 Barracuda failures within a year of purchase) - albeit I was using them for different purpose than backup. – njboot May 9 '15 at 19:32
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    I'm thankful for you sharing your experience and data. Also sorry you had bad results. My 3.5 experience is almost all seagate for non-bare drives (20+ and knock on wood) and all WD for DAS and bare drives. (One WD of about 10 failed after 4 months and warranty swap was trivial and speedy) – bmike May 9 '15 at 23:23
  • @bmike My experience with Seagate's drives are not as extensive as yours. After looking into it further, I may have just stumbled upon the “bad apple” of Seagate drives - that being the 7200 RPM barracuda. I have a DAS RAID set-up consisting 4x2TB WD Red drives and am very pleased with them. I thank you for your comments, as well as sharing your experience. I've updated my post to accordingly! Cheers. – njboot May 10 '15 at 6:35
  • Awesome. Also, I had one client with a Seagate drive that wouldn't spin up. We called and asked about data recovery and they allowed me to break open the plastic enclosure and hook the bare drive up to a sled and get the data, then they approved a warranty swap and replaced the unit under warranty for the client. Well above the service I expected. – bmike May 10 '15 at 16:39

You will need a drive at least as large as the internal storage of the Mac.

You can open About This Mac from the Apple menu at the top left of the screen and then select storage.

You probably have between 128 GB and 512 GB of internal storage, so getting a 1 TB drive would be room for double the space of the largest Air storage drive. You could also get away with a 500 GB drive in most cases. I'd say buy whatever size drive is in the middle of the price for the next size up once you select the case and connection you prefer.

Usually in the US, you can get a feel for when the drive becomes pricey by comparing: http://www.amazon.com/Elements-Portable-Hard-Drive-WDBU6Y0020BBK-NESN/dp/B00DULWSXI

  • 500 GB for $52
  • 1000 GB (1 TB) for $58
  • 2000 GB (2 TB) for $87

The 3 GB and larger portable drives will be an extra $50 or $100 so I buy right below the big delta price jump. Save $$ if you have modest needs - that 1 TB drive is a lot of storage for the cost.


Depending on what sort of backup you want to do: if you want to use TimeMachine the normal rule of thumb is that you choose a size that is 3 times the internal disk size. If you want to do a clone, the same size is enough, but you loose history. I propose to use a disk for TimeMachine as well as a second disk for a clone or another type of backup.


I would suggest that you use a portable drive rather than a desktop external drive.

With most Portables you will not need to worry about an extra Power supply.

I would also use TimeMachine with the device.

Be aware that TimeMachine will eat all available space on the drive overtime. And overwrite the oldest backups.

Which although this is ok I often find I want to back up somethings outside of Time Machine.

If you can afford a 2TB drive you can partition it into two MacOS Extended Journaled Partitions of 1 TB each.

This is easly done with the Disk Utility.app already on your Mac.

You can then use 1 partition for TimeMachine and the other for non Time Machine Backups or Storage.

Or split it with the TimeMachine partition using 1.xxx TB and the other partition the remainder space. i.e 1.5TB & 500MB

But I would let TimeMachine have a minimum of 1TB.

If you go for a 1TB drive then let TimeMachine use it all.

Others have suggested WD of HGT drives I agree with this and I have never had a problem with one.

I have always purchased the WD passport drives. My latest is a 2TB My Passport Ultra (USB 3). This is actually pre-formatted and intended for a PC.

And was cheaper than the ones intended for the Mac. It is a simple matter of reformatting the drive to a Mac one.

The PC drives come with a load of software that helps with backups, encryption and drive utilities. For PC and Mac (image shows Mac apps) Before you erase and reformat, copy these all off to you Mac incase you want them at a later date.

I have never really looked at them passed copying them off but you may find them useful.

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Do not use Lacie drives. I have found they will die on you no matter how nice they look.


If you do Partition into two drives you should make sure that TimeMachine does not Back it up by using it's exclude options to exclude the second Partition.

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    My experience with LaCie is mostly from PPC and early Intel days, but I found that they mixed whatever drive was cheapest and not knowing what rotation speed / manufacturer was inside their product was a deterrent for me buying from them as well. – bmike May 9 '15 at 15:49
  • I’m down voting this answer because this is poor advice: "If you can afford a 2TB drive you can partition it into two MacOS Extended Journaled Partitions of 1 TB each.” If you’re using an external drive for backup purposes, it should be used exclusively as such. Partitioning a disk so that one volume be dedicated to backup, another to whatever, is a recipe for logical volume failures. – njboot May 10 '15 at 6:50
  • @njboot i have never had an issue doing this and I would love to see your factual evidence that using Timemachine on a partition and splitting a disk like this is ill advised. – markhunte May 10 '15 at 7:09
  • @markhunte see the link provided or search the Apple Support Communities for endless Q's regarding the pitfalls of using a partitioned disk in this manner. – njboot May 10 '15 at 7:28
  • @njboot, I cannot see what you a saying in the link. It actually seems to say what I am saying. If you want to do this anyway, it's much, much better to partition an external drive into 2 (or more) parts, also called volumes. Assign one to Time Machine, for its exclusive use for backups; use the other partition(s) however you want. If you are talking about allowing TimeMachine to backup the second partition. I have not said or implied to do that. And I would advise to use the TimeMachine to options to exclude it. – markhunte May 10 '15 at 8:51

I don't want to spend lots of money on something if it's not entirely necessary.

Backups are necessary, as you have now realized. Drives are readily available for about $100 - is your data worth that much to you? (Drive-recovery services start at $1000)

There are now only 3 manufacturers of hard disk drives, and they all make reliable drives. There are, however, hundreds of external-case manufacturers and the quality ranges from (literally) bulletproof to complete junk.

I'm using a 13-inch 2013 macbook air with 4gb memory

That changes the equation quite a bit. You can plug almost any decent external drive into a desktop, turn on Time Machine, and then forget about it (I have a rack of LaCie D2 drives under the desk). But I expect you move the laptop around quite a bit. If you don't remember to plug in the external, activate the backup and wait for it to finish you probably won't have one when you need it.

Apple already has a solution for you. Get one of the Time Capsule backups / wifi routers, set it up on a shelf, and then forget about it. Your computer will back up automatically, over wifi, whenever it is plugged in. Doesn't even have to be open (it does of course have to be turned on). At $300 it's not cheap, but it does include wifi and it's fully integrated. You're buying convenience here. If you want to spend less you have to do more work.

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