Personal Digital Archiving Guide Part 3: Storage

Store display of commercially-available external hard drives

Digital storage options on display at an office supply store.

Photo by Scott Witmer.

Welcome to Part 3 of our Personal Digital Archiving Guide. For a quick introduction to digital archiving concepts, check out yesterday's Personal Digital Archiving Revisited. For more information, see the first two parts of this guide, Preservation Planning and Media Types and File Formats. Part 3 covers digital storage options for backing up your digital materials. 

First off, remember the 3-2-1 Rule for backing up your collection of digital files:

  • 3 separate copies
  • 2 different storage media
  • 1 stored in a different location

When considering different storage options, some factors may matter more to you than others. While digital storage has become less expensive over time, keep in mind that you're making 3 copies of everything, and that your digital collection (and storage costs) will continue to grow over time.

Recommended storage options:

External Hard Drives

External drives from commercial manufacturers, such as Seagate and Western Digital, are widely available online or at office supply stores. They run for around $50–100 for 1 TB of storage, and the cost-to-TB ratio goes down as storage capacity increases. Some drives may require a software installation, but once you've connected through USB or firewire, you can simply drag and drop your files to the external drive, or even schedule automatic back-ups using the software.

The quality of drives varies, so it’s a good idea to check the latest reviews or consumer comments about drive performance. Backblaze, a cloud storage service, publishes a quarterly hard drive reliability report [Q1 2018] based on daily statistics about the models they use in their data centers. Their drive requirements are likely to be much different from yours, but these reports can be an interesting snapshot of failure rates for specific populations of drives from a variety of manufacturers.

Cloud storage

There are many cloud services (Google Drive, iCloud, Dropbox), and many reasons to use them to back up your digital files: convenience, unlimited storage, access from any computer, and no physical media to deal with. However, there are a few things to keep in mind when you're deciding on a cloud service:

  • There is no "cloud." Your stuff is on someone else's computer, most likely a server farm. Where are these servers located? Cloud services often cycle data from one location to another in order to mitigate some of the risks of a natural disaster or other form of server failure, but it can be difficult to get details about where your data actually resides.
  • Getting your stuff out of a cloud service may be tricky. Cloud storage requires a reliable Internet connection. Many people live in areas with poor Internet infrastructure and may have difficulty downloading TBs of data when the time comes. What happens when you need to get all your data out at once? Does the service offer an easy option for downloading everything you've put into it?
  • Cloud costs add up over time. Many cloud storage services that start out free and only charge when you reach a certain threshold (2–15GB, depending on the service). What are the long-term subscription costs? What happens if you're unable to pay? 

Not recommended for long-term storage:

‚ÄčOptical media, such as writable CD-r and DVD-r discs, were once considered a good option for digital back-ups, especially the gold varieties which are marketed as "archival quality." But whereas optical drives used to be standard features of computer hardware, they have become less prominent as computing environments evolve. While some optical media such as blu-ray can hold up to 128GB of data, the average single-sided DVD-r holds around 4.7GB, making it a less attractive option for backing up a large digital archive. The long-term durability of writable optical media is also questionable, as data is stored on a dye layer that is vulnerable to deterioration over time.  In short, optical discs are fine for temporary back-ups, but may not be the best choice for long-term storage.

USB flash drives (aka thumb drives) are capable of holding up to 2 TB of data and can be rewritten thousands of times. However, their longevity is effected by cycles of rewriting and the limited durability of the USB head, so the long-term stability of a USB flash drive as a storage device is difficult to predict. And while their small size makes them convenient to carry around, USB drives are also very easy to lose. Like optical discs, USB thumb drives are good for everyday purposes such as transporting files or making temporary back-up copies, but should not be relied on for preservation storage.

Storing the digital storage

What type of conditions are best for storing your back-up storage media? The best way to think about this is to keep your back-ups in the same type of environment where you yourself are most comfortable. So, avoid temperature extremes and frequent temperature or humidity changes. Keep your hard drives in areas free from dust, bugs, water, or other potential environmental hazards. Also, you probably don't want to keep your digital storage devices near powerful magnets.

Don't forget: digital preservation requires active maintenance

True long-term preservation requires monitoring and maintenance over time. We don't know how long these storage devices will last. You can copy all your files to an external hard drive and stick it in a shoebox at the back of the closet, but there's no guarantee you'll be able to open those files in 10 years. No matter what storage media you choose, don't just back up your files and forget about them.

  • Check your media annually. Open up your storage media and test a few files to make sure they still open. If your files are stored in the cloud, download some samples and make sure they open as expected.
  • Refresh your storage every 5–7 years. Copy your files to a new storage media every 5–7 years to help mitigate potential failures from aging technology. This is also a good opportunity to reassess your long-term storage requirements, and get rid of any files you no longer need to preserve. If your storage media is still functioning after 5–7 years, there's no reason to throw it out, just make sure the content is also copied to a newer device.

Coming up next week on World Digital Preservation Day (Thursday, November 29), the UM Library Digital Preservation Unit will present our Pop-Up Digital Archiving Clinic in the Design Lab PIE Space at Shapiro Library from noon to 5pm. Stop by and ask us questions, marvel at our exotic floppy disks, and pick up a Personal Digital Archiving zine.