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The Care and Feeding of External Hard Drives

With the introduction of the new Mac Pro, Apple sent a clear message that it’s abandoning internal storage expansion in the Macintosh product line. If you need more storage for your Mac, you’re going to need some kind of external storage device, whether it connects via USB, FireWire, or Thunderbolt.

(Image courtesy of Roman Loyola. See “How Many Devices Can You Attach to a Mac Pro?,” 24 April 2014.)

And with the prevalence of fast but low capacity solid-state storage, you are going to need more room for data, and that means one or more external hard drives. Historically, external drives have been used more for backup than anything else, but when you’re relying on external storage as the primary location of important data, it’s essential that you take steps to protect that data.

Test Them First! -- I recently wasted an entire weekend trying to copy data to a new external drive, only to run into troubles later. The encrypted partition wouldn’t accept my password, or if it did, the Finder would prompt me to initialize the disk. In the worst cases, it would cause the Finder to freak out, forcing me to unplug the drive and reboot.

At first, I thought that it was because I was trying to do something fancy: share an encrypted volume over the network for my wife’s Time Machine backups. But after running the drive test included in WD Drive Utilities for Mac, I learned that no, the drive was just bad out of the box, and I’m having it replaced.

So, before you start copying your collection of HD movies over to your new 4 TB hard drive, run a thorough diagnostic test first to ensure that the disk doesn’t have excessive bad sectors or other problems. There are a number of utilities that do this, most priced at around $100, but the big-name drive vendors sometimes offer a free drive utility, often including it on the drive itself. There’s the aforementioned WD Drive Utilities for Mac for Western Digital drives, and Seagate offers Seagate Dashboard for Seagate Backup Plus, Seagate Slim, and Seagate Central drives. Check with your drive’s manufacturer to see if it offers a similar tool.

You might be asking, “Doesn’t Disk Utility do that?” Sort of. If you select the drive in Disk Utility, click Erase, click Security Options, and then move the slider at least one step to the right, Disk Utility will write zeros over the entire disk. Should one of those writes fail due to a bad sector, Disk Utility will map out that sector so it won’t be used. The same remapping should happen in regular use, but by doing it at the beginning, you can identify a drive that fails too many sectors. It is slow, and erases any data that happens to be on the disk, but it’s a good way to ensure that the drive is starting with a clean bill of health.

(The Verify Disk and Repair Disk options in Disk Utility’s First Aid view are useful, but not in this situation because they examine only the drive’s file system, and don’t exercise the physical surface of the disk in the same way. Use Verify Disk if you’re worried about filesystem corruption on your boot drive, and if you’re testing an external drive, click straight over to Repair Disk, since it does the same check, but fixes errors as it goes, saving you time.)

Back Them Up! -- Many people don’t back up their external drives, but, assuming you’re storing important data there, you simply must back it up. External drives fail more often as internal ones. Unfortunately, that means buying even more external storage, which isn’t cheap, but do you want to risk losing your precious photos, videos, documents, and music?

There are a few ways to back up one external disk to another. You could manually copy the contents of one to another in the Finder, but that’s crude, and like all manual backup schemes, guaranteed to fail eventually.

Apple’s Time Machine supports backing up external disks, but excludes them by default. To make Time Machine back up an external disk, choose Open Time Machine Preferences from the Time Machine menu, click Options, select the disk you would like to include in Time Machine, click the minus button, and click Save.

Alas, Time Machine combines your boot drive and external disk backups on the same volume. Imagine that you are backing up a 500 GB boot drive and 3 TB of media on an external drive to another 4 TB external drive, and later add on another 3 TB drive. As soon as you copy a significant amount of data to the new drive, you’d undoubtedly fill up the 4 TB Time Machine drive. Without moving to a RAID array or Drobo, you can’t even buy a drive that’s large enough for such a situation; so we recommend avoiding Time Machine for backing up external drives.

For more granular control, we prefer utilities like the $27.95 SuperDuper and the $39.95 Carbon Copy Cloner (CCC). These tools make exact duplicates of a disk, and can be set to run automatically. I personally use Carbon Copy Cloner, set to “Temporarily archive modified and deleted items,” which moves items on the duplicate drive that have been deleted or modified on the primary drive to a special _CCC Archives folder, until they take up too much space or are too old. By default CCC starts deleting old archives when there is 15 GB of space free on the drive, but you can modify this in settings. That way, if I accidentally delete a file from my main storage drive, Carbon Copy Cloner doesn’t delete it immediately on the backup, so I can recover it later.

Also consider backing up your external storage with a cloud backup service like CrashPlan or Backblaze. That way, if your drives are stolen or are lost in a disaster, your data will still be recoverable. As a bonus, both services offer iOS apps that let you access your files on the go. If you want to back up massive amounts of data, CrashPlan offers a $124.99 Seeded Backup service, and a $164.99 Restore-to-Door service, both of which let you sidestep slow Internet transfers by shipping a hard drive.

For more detailed information on all these backup technologies, read Joe Kissell’s comprehensive “Take Control of Backing Up Your Mac.”

Hide Them! -- You probably don’t want every disk mounted at all times. The duplicate of your boot drive, for instance, doesn’t need to be mounted until you need it (and Carbon Copy Cloner and SuperDuper can mount and unmount drives automatically).

If you have another drive you don’t want on your desktop at all times, the solution is to unmount it, which removes it from sight, but lets you remount it later. The standard way to do this is by selecting it in the Finder and clicking the eject button or pressing Command-E (or drag it to the Trash in the Dock, or Control-click it and choose Eject — you get the idea). To remount it without messing around with hardware, select it in Disk Utility and click the Mount button in the toolbar.

A better solution is the $1.99 Mountain utility, which lives in your menu bar, letting you mount and unmount drives with the click of a button. You can also mount and unmount all volumes with a keyboard shortcut.


Unfortunately, Mountain’s developer, Appgineers, got caught in Apple’s changed sandboxing requirements for Mac App Store apps, making it impossible for the company to update the app in the Mac App Store. To get a current version, purchase Mountain from the Mac App Store, open it once, close it, download the trial version from the Appgineers Web site, and copy that to your /Applications/ folder, overwriting the Mac App Store version.

That’s my only beef with an otherwise fantastic and cheap utility. As a bonus, it also tells you which apps are preventing you from unmounting a disk. It’s essential functionality that Apple should roll into Mac OS X.

If you want to automate mounting and unmounting, try the $36 Keyboard Maestro, since it can execute Unix shell scripts. Don’t worry — these are easy. To make a macro that unmounts a particular drive, perhaps at login, use the Execute Shell Script action to run this text script:

diskutil unmount “/Volumes/driveName”

And if you want to mount a particular drive with a keystroke-driven macro, use this script:

diskutil mount driveName

Speed Them Up! -- Are your external volumes slow, do they keep making noise even when not in use, or do they stubbornly refuse to unmount? One common cause is Spotlight indexing. You’ll probably want to let Spotlight index a storage drive that contains useful documents, but there’s no reason to index backup drives.

To prevent Spotlight from indexing a backup drive, open the Spotlight pane of System Preferences, and, in the Privacy view, either drag the volume in from the Finder or click the plus button and select it.

This should make your drives more responsive, avoid wasting CPU cycles unnecessarily, and make your office a bit quieter.

Encrypt Them! -- One of the best features of Mac OS X is full disk encryption, called FileVault 2, and I keep all of my disks encrypted. If thieves steal my drives, I don’t want them to be able to access my photos and financial information. Apple introduced FileVault 2 with OS X 10.7 Lion, and with 10.8 Mountain Lion, moved the encryption commands into the Finder’s contextual menu. The only downsides to FileVault 2, apart from the requirement that you remember the login password that’s used to decrypt the data, are a very slight performance degradation and more difficult drive recovery (but you have a backup, right?).

To encrypt a drive, Control-click it in the Finder and choose Encrypt driveName. You can continue to use it normally once encrypted — but the data is protected if a bad guy were to get his hands on the drive. If you decide you want to decrypt the entire drive later, Control-click it and choose Decrypt driveName.

Both processes can take a long, long time, so it’s best to encrypt a disk before you have any data on it. It may be faster to move your data to another volume first, erase and encrypt the original volume, and then move the data back. Make sure you have a backup first!

Keep Them Cool! -- A lot of external drives don’t come with fans, which makes them quiet, but which also means that they run hot. Most drives are rated for up to 50 or even 60 degrees Celsius, but it’s worth putting a little effort into making sure there’s good airflow around the drive cases to aid in cooling. Drives won’t wilt at high temperatures, but the likelihood of failure goes up, particularly with older drives, and other components in the drive are also more likely to fail.

Keep Them Powered! -- Do you ever sit down in the morning and see the nasty “Disk Not Ejected Properly” error? Assuming gremlins didn’t unplug your external drive in the middle of the night, that means that, for some reason, the drive lost power or its connection, either of which could lead to disk corruption. There are two ways to address this: one in software and one in hardware.

First, make sure that Mac OS X isn’t putting your drives to sleep. Open the Energy Saver preference pane and deselect “Put hard disks to sleep when possible.” For reasons I don’t entirely understand, putting the disks to sleep automatically sometimes causes them to power off completely or lose their connection. Disabling this setting also eliminates the annoying wait as a drive spins up.

Next, if your external drives are powered by a wall outlet, you should invest in an uninterruptible power supply (UPS), which is essentially a surge protector with a big battery inside. With the UPS providing power in the event of a power failure, your drives will stay powered up until you turn them off gracefully, or at least as long as the UPS battery lasts. You can purchase a UPS from Amazon (like the low-end APC Back-UPS BE350G) for as little as $40 that’s likely sufficient for a laptop and an external drive, but if you have a desktop Mac, you’ll want a UPS with a larger battery (like the APC Back-UPS BE750G, which is about $83 at Amazon) that can protect your entire system.

Return Them! -- Drives die, and with the industry succumbing to the market’s desire for bigger, cheaper drives, they die all too often. But what many people don’t realize is that drives often come with full replacement warranties. If you’re buying a drive in a case, such as from Other World Computing or Granite Digital, you’ll want to contact that company first, but if you’re buying a bare drive and installing it yourself, or if the case vendor won’t help, check out the mechanism’s warranty.

TidBITS staffers have returned numerous dead drives over the years, and it’s generally an easy process. You simply fill out an online RMA form (which tells you if your drive is covered or not), ship your drive back, and wait for the new one to arrive. You’ll usually pay shipping costs to return the dead unit, and you’ll get a replacement that’s identical in capacity.

The only remaining hard drive manufacturers are Seagate, Toshiba, and Western Digital (the links go to their warranty systems), so if you have an older drive from another brand that might still be under warranty, check the full list of defunct hard drive manufacturers to see which of today’s three you might talk to about warranty replacement.

The Wisdom of External Storage -- After I moved back to the Mac from the DIY PC world, I was frustrated by the limited amount of storage available in Apple’s computers. In my old tower, I could slot in as many high-capacity drives as I needed.

But when my MacBook Pro recently developed an audio problem that requires a logic board replacement, it dawned on me how useful it is to have my data stored outside my computer. Instead of being without my data for a few days, I can borrow my wife’s MacBook Pro, plug in my USB hub, restart with my bootable duplicate, and get back to work like normal — albeit a touch slower.

My only lament is that Apple was slow to replace the poky USB 2.0 with the faster USB 3.0 standard, and the Thunderbolt peripherals we really want remain unaffordable for the average user. But my hub and drives all support USB 3.0, as do all of Apple’s current Macs, so when I eventually upgrade I’m due for a major speed boost. And when I do sit that new Mac down on my desk, all my data will be waiting for me, one plug away.

Check out the Take Control ebooks that expand on the topic in this article:

Joe Kissell provides the advice you need to create a Mac backup strategy that protects your data and enables quick recovery. He compares backup software, services, and media to help you make the best choices. You'll learn to set up, test, and maintain backups, plus how to restore files after a calamity! Don't miss our new Joe of Tech comic!
Regular maintenance is necessary for peak performance and to prevent problems, but it's hard to know what to do and when. Best-selling author Joe Kissell walks you through his commonsense approach! Updated to for 10.8 Mountain Lion (including the just-released 10.8.1!) and the latest versions of Joe's recommended utilities.


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Comments about The Care and Feeding of External Hard Drives
(Comments are closed.)

JohnB (SciFiOne)   2014-04-28 09:08
Good article. Do you know who makes the cores on LaCie drives and IOSafe drives? I've never had a LaCie fail, but every IOSafe has failed (I eventually gave up on them).
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-28 11:30
I don't know exactly what mechanisms are inside those drives, but there are two possibilities for the problems:

* The units you bought had a run of bad mechanisms from the same company. All drive manufacturers seem to go through ups and downs with reliability, sometimes even within the same model.

* There was something in the IOSafe case or power supply or controller that made them more likely to fail, at which point the mechanism inside may have been unrelated.

All that said, depending on when you bought those drives, they may have used Seagate mechanisms, since it's now owned by Seagate.
Seagate bought La Cie recently. But La Cie has been using Seagate or other brands previously. No way to tell which you have.
BTW: Hitachi sold its 2.5 inch business to Western Digital but it's 3.5 inch to Toshiba.
JohnB (SciFiOne)   2014-04-28 19:32
I think I got a different case back each time they replaced it. Oh Well. I now use a small external that I store in a FP, WP safe instead. Much easier and cheaper and I can have more than one.

Article suggestion: Something simple on RAIDs. I've never understood those.
I had a Lacie Porsche drive fail after falling from my dad's filing cabinet. It was out of warranty, but I cracked it open and it was a Maxtor drive, still under warranty, so I did an RMA on the drive and got a new one in a couple weeks :)
Gerald Shields  2014-04-28 14:29
One problem with your article: You can and should also consider purchasing a Network Attached Storage device or applicance (NAS for short) to do you backup and storage needs. I've got a Synology DS213J and though it's a Linux NAS, it seems to work well with Macs and you can adapt it for other uses: (Ex: You can set it up as a iTunes Server). Of course, if money is no object, get a Apple Time Capsule too.
Josh Centers  An apple icon for a TidBITS Staffer 2014-04-28 14:35
While I would like to do that, it's also considerably more expensive, and outside the technical realm for most users. Just about everyone keeps data on an external hard drives now, so that's what will help most users.
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-28 14:47
A NAS is a fine solution for some of this stuff, but a topic for a different article. :-)
Gerald Shields  2014-04-28 15:17
I don't know. Most external HDDs cost between $60-$100 bucks and the NASs tend to go between $150-$400 or more. However, I think the NASs are more reliable (You won't go wrong with a Synology device. A lot of Mac users use one and the GUI is fairly Mac-Like and the add-ons are painless to install) and let face it: An Apple Time Capsule doesn't give you any "lip", it just does the backup job! Another thing: An external drive means you got to connect the drive directly to your Mac. A NAS just needs to connected to your router, thus if you got multiple Mac or PCs (This also extends to gaming machines like the Sony Playstation or Streaming Media Players like AppleTV or an "iDevice" like the iPhone or iPad), they all can use the NAS as a resource on you home network.
Gerald Shields  2014-04-28 15:34
I understand. I only wish was to expand the author's options.
Mike Cohen  2014-04-28 16:33
I've been using Drobos for several years (currently a Drobo FS) and I love them. Last year, one of the drives went bad (as all drives do eventually). The Drobo alerted me & I replaced that drive without shutting down and I didn't lose any data.
Marcia Blake  2014-04-29 09:18
> A NAS is a fine solution for some of this stuff, but a topic for a different article. :-)

Indeed it is. Erm, when may we expect to see it? :-)
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-29 09:24
We'd need to find an appropriate author - I don't think anyone on staff (with the exception of Joe, perhaps) has much experience with NAS units.
Elliott Landy  2014-06-05 03:57
One problem with NAS, as far as I understand, including synology, is that some of their backup info is not normal mac file structure and I know of a tech firm that could not get their data back due to the synology non standard backup structure. I would like to know of an nas which uses only mac standard file structure. Drobo would also have non standard files structure.
Kirk Friggstad  2014-04-28 15:22
Semulov is a freeware alternative to Mountain - I don't know how often it's updated, but it's still working on my Mavericks system.
Jonathan Miller  2014-04-28 16:20
What annoys me and is probably beyond the purview of this article but I don't know where else to vent is that when I want to buy a new hard drive from Amazon, NewEgg or wherever, there is no listing of the manufacture date. I once purchased a "new" hard drive that was 2 or 3 years old (I returned it, of course). And Seagate has some arcane date code that one needs an engineering degree to decipher (or at least they used to). Hard drives have a life expectancy of about 5 years (I think) so I when I purchase one I want to know when it was manufactured. Thank you for letting me vent.
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-29 07:31
You're welcome! I would be very surprised if most drives were on shelves for long, particularly if you're buying from a high volume reseller like Newegg. That's especially true after the problems the industry had after the flooding in Thailand in 2011 - from stories I've heard, I'm sure nothing was left on the shelves then.

And that said, drives will have a mean time between failure rating, but that's only going to apply to time in use. Just sitting on a shelf shouldn't cause a drive to age in a significant way, I wouldn't think.
Alan Sanders  2014-04-28 16:37
One issue with hard drives replaced under warranty is that both Seagate and Western Digital routinely replace problem drives with refurbished units that are covered by warranty for only 90 days. If your Seagate Backup Plus, which comes with a two-year warranty, fails after a few months or even after a year or more, you'll end up being short-changed on warranty coverage if the dead drive if replaced with a refurb that is only covered for 90 days.
Tom Robinson  An apple icon for a TidBITS Contributor 2014-04-28 19:03
That would depend on where you live 8-) In New Zealand, depending how much goods cost and a few other factors, they must be 'durable - last for a reasonable time'. i.e. if you pay a good price the goods should last for a good time. Doesn't matter what the warranty says.

The few times I've had La Cie and WD drives replaced, I've always received brand new units in boxes.
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-29 07:32
You're absolutely right about replacements being refurbished drives - at least one of the vendors I was looking at while working on this article was clear about that. But I don't really know how to evaluate what a refurbished drive really is, since these things are so cheap, it can't be worthwhile to do any kind of significant repair on them. I've never had a replacement drive fail that I know of.
Michael Paine  2014-04-28 22:23
Thank you for the tips.
I have started using an external SSD drive for a bare-bones time machine backup of my macbook. Although Time Machine provides alternate backups for multiple drives I was disappointed to find I could not customise the backup to the SSD drive to cater for its limited capacity. See the discussion I started here:
I have also been playing with booting an old iMac from an external SSD drive:
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-29 07:35
I agree that the advice in the post is correct - a bootable duplicate makes a lot more sense than Time Machine in your case. I'm not sure there's a real win in using an SSD for backup though, since the speed doesn't really help much there. As a boot drive, it's a lot more useful - neat work with the external approach.
I have to disagree with the premise of the article. Yes, external drives for backups. But due to the parsimony of the Dean (and Apple) I've now got a lovely 13" Retina with a measly 250gb HD. iPhoto and iTunes onto an external hard drive. The constant connecting and disconnecting, the loss of those two when I go to work or travel—it's all a stupendous pain and certain some day to cost me. There is no reason that internal HDs cannot continue to grow, and I desperately hope that you are wrong about the PRO signifying the future of all Apple machines.
Adam Engst  An apple icon for a TidBITS Staffer 2014-04-29 07:37
I hate to say it, but all signs point to us being right in the short term.

In the long term, SSDs will increase in capacity and drop in price, and it won't be an issue any more.

Or, we'll have fast enough connectivity and cheap enough online storage that the things that cause most people to need extra storage (videos, music, and photos, probably in that order) will be stored online.

So it's only a matter of time, but until then, I feel your pain.
Stuart Hertzog  2014-04-29 07:37
An emerging problem is the difficulty of finding external drives with the FireWire 800 interface, needed by older computers w/o USB 3. Even external case manufacturers have forsaken FW 800 for USB 3. Any suggestions about sourcing FW 800 drives or cases?
Howard Mullinack  2014-04-29 16:32
Other World Computing

Their current lineup includes drives with FW800 and USB3, so that when you get a newer computer that doesn't have FW, you are still in the fast lane.
Paris Voutetakis  2014-04-29 21:28
I would add in this article and the line of comments two new ones that thin are worthing:
- Having a good Time Machine policy (with the latest versions you can keep separate backups automatically on several different physical locations) in the event of loss of your Mac you can have your new one up and running in a couple (or up to several) hours exactly the way you lost it and with the added benefit of having upgraded to a new one (if you are a lucky corporate user that someone else is paying).
- Even NAS drives do fail. The unl icky situation about that is that most of them (at least the ones that occur ed me) rely on some flavor of Unix (or Linux) therefore their file system is probably alien to most users (Ext 2, 3, or 4 ) and in the event of failure to recover the files is beyond hacking, even worse if the company that made it is out of business or even it is in warranty time.
Storage solutions follow the trends of the rest of computer industry so any lifelong conclusions are futile
Mark Fuccio  2014-04-30 20:46

Nice article and good comments. Let me add mine here:

1. Zero-ing a drive, by writing 0's in all blocks as described above, is a good practice of new drives. Its a way to stress the drive before putting it into service. Drive reliability follows a "U" curve, i.e. early failures (infant mortality failures related to manufacturing issues), then a period of reliable service, then failures due to age. Studies published publicly by Google or Backblaze -- Google for them -- show that the initial down leg is about 6 months, the bottom of the U is several years, and the upward curve runs until the drive fails.

2. In addition, reading every block on a drive is beneficial. Why? Any read errors that the drive controller finds cause the drive to correct the error using redundant, error correcting code information stored on the drive.

Reading every block on a drive is tricky. If you are comfortable with Terminal, then say so in the comments and I'll paste some things you could use.

Backblaze or Google uses thousands of hard drives and burn through them monthly. And Backblaze gave a very good rating to the WD green drives! Seriously? Those were the reason alot of macs had issues because of the energy-saving features of the green models and slower spindle speeds.
Formatting a new drive (zeros) has never been a bad idea, but no one thinks about it as zeroing out a 4TB takes hours.
Buying HDDs from Newegg was an issue for me. Great prices but poor packing.
I like to warn people that getting an external 2.5" USB bus-powered HDD can be a gamble: those drives are made of glass (not alloy platters). You drop one, it can shatter. Also, recovery of some is impossible as the controller encrypts on the fly, plus it has integrated micro-USB (not sata to USB) on some.
I prefer OWC or Wiebetech chassis and putting in my own (7200 or red/black model) drives.
Having a time capsule, a clone drive and a NAS Raid 6 along with encrypted cloud for small files is ideal.
nichtdiebohne  2014-05-05 06:47
Sorry, Nothing wrong with ads on websites but redirecting (aka hijacking) the iOS browser to open the AppStore app is unacceptable.
Adam Engst  An apple icon for a TidBITS Staffer 2014-05-05 13:46
We just use Google AdSense to display ads to those people who aren't TidBITS members (those who are get an ad-free site), but I'm not aware of any particular ad doing this. If you can share details about what the ad was for, I can block it if it's egregious.
Josh Centers  An apple icon for a TidBITS Staffer 2014-05-05 13:46
Which ad did that?
Jonathan Duke  2014-08-07 09:47
I “build” my own externals-that way I know and get exactly what I need and want in the drive. I have only two criteria for the enclosures I select: fan-cooled and able to support large (≥4 TB) drives.

While it isn’t necessarily less expensive than buying a pre-built external, there are fewer questions, problems (I hope) and longer life of the drive (and hence my data). And, the option is available to go with a larger drive in the existing enclosure later.

Additionally, whether I’m buying off-the-shelf or building, I use SoftRAID to certify the drive prior to use. It will run a full-volume scan of the drive and then run some additional tests. It does take a while-a 4 TB drive might take up to 3 days (over USB), but I know that I’ve got a drive that shouldn’t fail a few days or weeks into use. While the certification isn’t a guarantee that the drive won’t fail, it does weed out those that will fail early. Additionally, I also get the option to return a drive to the point of purchase and recieve, hopefully, a new unit as a replacement versus a refurbished/remanufactured unit later on.