Dos and Donts for managing data on external hard drives

USBDriveIconXYour data is the most important aspect of your computer, and unfortunately we often don’t realize this until we’re faced with the possibility of having lost exceptionally valuable (if not priceless) work. This can happen as easily as a computer suddenly shutting off on you and no longer booting, or when you attach an external hard drive containing all of your files, only to find it will not mount and cannot be repaired.

At these moments of realization, you’re confronted with limited options. Therefore, the best approach is to ensure you never get to this point, at least from the standpoint of your data, and the easiest way to do this is to always keep a copy of your data on more than one physical device. Whether you employ Time Machine, manually copy files, use a system cloning tool, or another routine, provided the data is duplicated to at least one secondary volume then you greatly reduce the chances of it falling victim to a hardware failure. The formula is easy:

  1. Get an external drive with the capacity for all of your data (At least the same total capacity of the drive currently storing your target data).
  2. Set up a backup routine (Time Machine, a clone, etc.) using the drive
  3. Repeat steps 1 and 2, preferably keeping the drives in different physical locations
  4. Consider using OS X’s drive encryption routines to protect your data from theft

When looking for a device to handle your data, you will be confronted with a number of possibilities, including a plethora of brands, single-drive and multi-drive setups, connection technologies, formats, network storage, and more. So how do you choose?


Most modern USB hard drives, and especially those from reputable manufacturers (Western Digital, Seagate, Toshiba, LaCie, etc.) will be fully compatible with your Mac’s hardware and OS X. There are very few modern drives that are built for one platform but which will not work on another. Nevertheless, for any device you are considering buying, be sure to check for such compatibility limitations, and if you find one, then consider avoiding it. Even if the device is built only for OS X, this means you may have trouble accessing files from it if you only have a Windows-based system at your disposal. Furthermore, a drive that is built just for a Mac will offer no advantages over a similar drive built for all platforms.


Once you know the capacity of drive that you need for your data, there are generally two aspects to consider for an external hard drive, its physical size, and its speed. Overall, small portable drives are convenient, but break easier. Expensive drives may be faster by using SSD with the latest USB or Thunderbolt technologies, but often these are simply not needed unless you plan on doing extensive and regular data transfers to the device.

For the most part, other bottlenecks in your data workflow will prevent you from fully using a fancy external hard drive’s capabilities. Technically you can get an external SSD (even a striped RAID of two or more SSDs), and connect it to your Mac via Thunderbolt to give you a drive as fast as your Mac’s internal drive, but this is overkill unless you plan on using the drive as an active workspace. For basic and longer-term storage, a conventional hard drive will suffice and give you greater storage with acceptable speeds, for far less.

Dos and Donts

Regardless of your choice of drive, there are several dos and donts for setting it up, that will help ensure the drive and your data stays free from problems as you use it.

Don’t: Upgrade internal hardware

You may be tempted to try replacing your Mac’s internal drive with a faster or larger drive. Unless your Mac’s drive is failing or the Mac specifically supports drive upgrades, then it is best to leave the system as-is and rely on external storage for adding capability. This is especially true for systems that are still under warranty.

Do: Freshly format your drive to an OS X-native format

Most drives come formatted to either NTFS for internal drives, or the universally supported FAT format for external drives. While these can both be read by a Mac, with FAT being both readable and writeable, they are not the most compatible with OS X. Your best bet for data stability and security is to format the drive to the Mac OS native “Journaled HFS+”, which appears as “Mac OS Extended (Journaled)” in Disk Utility. Journaled filesystems offer transactional writes, which ensure data changes are fully written before committing them. If not, such as in the case of a hang or power outage, then the partially written data will be discarded.

Don’t: Install manufacture-specific drivers for standard drives

If your drive device is a standard single-drive setup (ie, it is not a RAID array), then you should not at all need special drivers for using it. By installing drivers that are not part of the OS, you chance an update to either the Mac OS or the driver may break something. In most cases the drive you have will work just fine (and perhaps better) without the manufacturer’s drivers or management software. The one exception to this is for RAID drives, which may require tools from the manufacturer to manage.

Do: Store all of your data in at least two different locations

Regardless of the other dos and donts suggested here, the most important thing you can do for your data is to keep updated copies of it on completely separate devices. You can do this by way of a Time Machine backup or clone, but if your backup drive is simply a partition of your main boot drive (ie, you split your drive in half using Disk Utility), then you chance a hardware failure knocking out the backup along with the original data. Therefore,

Drive recovery tips in the event of failure

Provided you have your data replicated and encrypted, a hardware failure or loss of a drive will not be an issue, as you can always purchase a replacement drive. This is the proactive key to data security. However, if your drive is showing troubles (specifically errors and warnings), then try once using Disk Utility to check for and repair errors. If you cannot make the drive at least readable with these routines, then unplug the drive and consider how much you need the data on the drive. If the data is ultimately not important but you would like to try recovering it for convenience, then you can try using third-party tools and additional resources to recover the data. If the data is essential and irreplaceable, then your best bet is to leave the drive alone until you can contact a proper and reputable data recovery service.

The one caveat here is encryption. If your drive is encrypted and you cannot unlock it either from a hardware failure or loss of a password or other recovery keys, then the drive is effectively wiped. You can set it aside in hopes you can remember the password, but if not then you might be best off by just formatting the drive and setting it up again. After all, it is just effectively an empty drive you have at your disposal.

17 thoughts on “Dos and Donts for managing data on external hard drives

  1. MaX

    Reputable manufacturers? Check out:

    Who makes the most reliable hard drive? Latest BackBlaze survey claims to know

    1. Randy S.

      The problem with the BackBlaze study is that it was done over a number of years and the hard drive industry changes very quickly. It may be worthless to know what brand was the most reliable three or four years ago.

      For instance, Hitachi comes out best in the BackBlaze study, but a few years ago Western Digital purchased the “HGST” name, but the rest of Hitachi’s hard drive business was sold to Toshiba. So, do you suppose that a Western Digital hard drive with the HGST name on it, but having nothing else in common with the Hitachi drives of a few years ago, is as good as the Hitachi drives that came out on top in the BlackBlaze study?

      1. Randy S.

        Of course, the BackBlaze study was of internal drives only. Not external hard drives. There are a surprising number of external hard drives on the market currently that are disappointingly unreliable. And that’s mostly due to their case design and supporting electronics. The big name manufacturers of internal drive mechanisms seem to have the most unreliable external hard drives. Their quality control appears to be almost totally lacking.

        Other World Computing offers decent external hard drives at good prices.

        The very best external hard drives that I’ve found, that don’t have astronomical pricing, are from Glyph. They also have excellent service and warranty (including free data recovery!).

  2. MaX

    How many drives have FAILED (wear and tear) due to an excessive backup routine (besides energy consumption, heat, noise, etc)? Shocking! Best backup strategy:

    – Full monthly backup with Time Machine. For instance on large external disk.
    – Daily backup of personal data only since latest full monthly backup. For instance on fast SDXC.

  3. Jim Chaffin

    I suspect there is not really a “best backup strategy” for _everyone_. 😉 A ‘monthly’ backup may be useless for people who made major additions to their software library the day after their last monthly backup. “Personal data” may not always be known to the ‘person’ and keeping up with which plists (and dozens of other app specific, but background files) changed can take a great deal of time, assuming one knows of all the changes.

    The info on why drives failed might be useful. The BackBlase data is as close as we may get to it, however. Their info is probably best for evaluating running a drive 24/7/365, however.

    The only thing as bad as _no_ backup is a backup that is out-of-date or that doesn’t have what you need on it. 8+O

  4. B. Jefferson Le Blanc

    With external drives my experience over the years has been that the bridge in the drive housing fails far more often then the drive within it. Which brings up one more problem with inexpensive drives: some of these are integrated with the case and the bridge so thoroughly that you cannot separate the drive from the case in order to use it elsewhere. Then there’s the problem with replacement cases: not long ago I had a Seagate drive die due to bridge failure and discovered that Seagate does do not offer replacement cases.

    The best source I’ve found for replacement cases is Otherworld Computing ( However, theirs are not generally the least expensive alternatives. Nor are they any more reliable than cases found elsewhere. But Otherworld has excellent warrantee policies. And they have a good selection of cases with a variety of interface options.

    Amazon no doubt has the largest selection of external drive enclosures, but their search results throw up everything but the kitchen sink, no matter how specific your search terms. So you’ll really have to hunt for what you want.

    All this supposes, of course, that you are handy with a screwdriver and are willing to open up a failed drive to test it outside the case. For this you will need something like the Newertech Voyager, a “toaster” in which you can place a 2.5″ or 3.5″ hard drive. The least expensive model is USB 3 only. For considerably more money you can get them with additional ports for FireWire 400/800 and eSata. If your computer supports USB 3 then the inexpensive ($29.00) model will probably suffice. It’s also a good tool for making archive backups, say those you’ll put in a safe deposit box, for which a bare drive will serve quite well. Apropos of which, I also use NewerTech StoraDrive anti-static cases for 3.5″ Hard Drives. This is a good idea if you’re going to put your backup drive in a metal safe deposit box drawer. I am currently using a 6TB drive partitioned so that I can back up my boot drive and several data storage drives on one device. Among other things, this saves on safe deposit box fees. Of course the location of your safe deposit box makes a difference. A bank vault is pretty much disaster proof and is generally climate controlled. Other locations may be more problematic.

    Of course no one backup strategy will suit everyone. But almost any backup strategy is better than none. Yet, I’ve found people using all but useless strategies, like updating a cloned backup only once every three or four months, or connecting their Time Machine drive once a month. It’s important to understand what you’re doing and why.

  5. msadesign

    A bit off topic, but Topher’s admonition not to replace an internal drive caught my eye as I have a late 2013 iMac that runs inexplicably slow (all the usual stuff checked, lots of ram). It runs so slow I wonder if the internal drive is the culprit, but changing that drive involves removing the screen from the computer and I am not anxious to do it.

    What I DON’T know: can the system use a USB 3/ Thunderbolt drive with the same speed as the internal drive?

    1. MrMurf

      Have you run DiskWarrior? If your disk’s “directory catalogue” is fragmented over 30%, things will really slow down. An SMC reset can also sometimes help.

    2. B. Jefferson Le Blanc

      An external USB 3 or Thunderbolt drive may run your system as fast as makes no difference. And probably faster, given what you say about how your internal drive is running now. If your budget can take it, an external SSD TB drive would probably give you the best performance. Bear in mind that on a 2013 iMac you only have Thunderbolt 1, rather than the TB 2 available on newer Macs. That said, a USB 3 SSD would work well and cost less than Thunderbolt. An external USB 3 HHD will do well enough, I suspect, and cost even less, while providing more capacity choices.

      1. msadesign

        Thank you to everyone who replied. In the end I took the machine to the Genius Bar; said Genius ran the proprietary apps that assured us both that there’s nothing wrong with the software, and that a re-installation of El Capitan would fix the problem.

        Which it did. The solution is unsatisfying, though, as the underlying issue remains unidentified; and restoring is a PITA when Time Machine cannot be used for fear of reintroducing the problem.

        The machine runs fast now, and I do appreciate the info about SSD.

  6. John

    Thanks for sharing this. With so many options available for external drives, I was happy to see you lay out some of the details to look out for when considering which to go with. I also agree with your suggestion to have at least one extra copy of the data stored in a separate location. Having the extra copy to fall back on can be a major key to making the data recovery process considerably smoother, as long as it is updated any time there’s a change to the data.

  7. Kathryn Jenkins

    I guess the advice to NOT change the internal drive shows how far the “good” silver Mac Pro has fallen: changing and adding internal drives is wonderfully easy with those machines. I won’t give mine up until there is a viable alternative—which may be never.

  8. MaX

    Hi Topher. I hope all is fine, since we have no news since 18th May 2016, more than three months ago.

  9. Deezy

    My Rule: NEVER buy just one external drive, buy two of the same size. Mechanical drives are designed to fail at some point, it is only a matter of WHEN. You should buy two external drives, and use them both religiously.

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