File Backups – Checking for Copy Errors

One of my “safer at home” projects is updating my file storage system. The drive I put new camera captures on was getting close to filling up, so I needed to expand my system by purchasing a 8TB Seagate external drive that could hold the contents of a partially full 6TB drive, along with the contents of a partially full 2TB drive.

It took me many hours of copying with CarbonCopyCloner to transfer the files from both drives to the new 8TB drive, which always tests my patience, and my tendency to want to watch the pot to see if it’s boiled.

With the copy complete, the next to do is a major reorganization of my folder structure to better fit my current needs and to work with my backup scheme. As part of this, I’m going to erase and reuse some older backup drives, but before I erase those drives, found myself with a nagging question. Did my computer actually copy all my files correctly to the new drive?

Most file copy operations, including what I did with CarbonCopyCloner, are optimized for speed. They read the file from one location and write it to another without verifying that the file was written correctly. Verifying a copy would take re-reading each file and comparing them, which would take a lot more time. In the case of my 5.5TB of data, it would have to read 11TB total of data. 5.5TB on the original drives, and 5.5TB on the copies.

Since my copies weren’t verified, it’s entirely possible that when I copied my files to this new drive, files that hold decades of work, valuable drum scans, irreplaceable originals and memories, that some did not copy correctly, and I could be losing some data. I used to accept that risk in the past, but experience has made me less willing accept it going forward. So what to do then?

CarbonCopyCloner has an option to compare your backup with your original, but for the size of my archive, it was going to be a very time consuming project, and difficult to organize. Fortunately I remembered Lloyd Chamber’s IntegrityChecker software that was designed to do just what I wanted.

First a couple lines about Lloyd and why I’m trusting his software to check my files. Many years ago I met Lloyd when he attended one of my workshops. He was using 8×10 film at the time and trying to push the bounds of what it could achieve…no minor feat. His film was of fantastic quality, but he was still not satisfied. He’s the type of person who obsesses over details in a way I greatly appreciate. But he’s not just a photographer. He has a couple patents to his name for compression technology he used in his very popular DiskDoubler and RAMDoubler software. He has the knowledge and experience to get very deep in the weeds of some interesting computer and digital imaging problems, and he blogs about lens and camera testing at diglloyd.com.

IntegrityChecker validates files in a very unique way. It creates a cryptological hash for every file on a storage volume that can be used to check if the file has been changed in any way. This lets you check the integrity of files and backups in the most efficient way I know how.

So now I’m in the process of creating hash files for my “original” disks. Once all the hash files are created, I’ll use those to validate that my multiple backups are faithful copies of the “original.” That will let me have peace of mind that I have good copies of all my files, and let me decide which copies are redundant so I can re-use those drive.

This kind of integrity checking is something we should all do, but since it’s not built into the operating software we use, it doesn’t happen unless we seek it out. If this is something you’re interested in, check out IntegrityChecker on Lloyd’s website.

I think it’s important to note that this is more of a “expert” level tool. It’s offered in both GUI and command line versions, and it’s going to take some understanding of the underlying principles of what it’s doing if you want to apply it correctly. Because of that, it’s not a tool for everyone, but it’s one I wish I had started using a lot sooner. For now it’s the easiest way I know to ensure my files copy correctly and don’t change once they are copied. Check it out and see if it belongs in your toolbox.

Don’t upgrade your software during Corona Virus!

Right now as we’re all on some sort of lockdown for Corona Virus and many stores and services are limited, I’m recommending you don’t update your software, particularly system software.

Updates don’t always go right, and sometimes they can take down your system. If that happens you might be stuck without the use of your computer, phone, or favorite software for an indeterminate amount of time.

I learned this the hard way many times over in my years of managing the servers and IT at West Coast Imaging. So much so that I set up rules for when I would never start a upgrade or major IT project. Here’s a few I can remember off the top of my head:

  1. No upgrades in the week before a trip. Having your system down when you are trying to focus on a trip is a real drag.
  2. No upgrades before a major project. My workflow is carefully validated to produce the results I expect. Software updates can throw kinks into that workflow, and that’s the last think I want when working on a deadline project.
  3. No upgrades going in to the weekend. I spent too many weekends at work over the years. Don’t set yourself up for a problem that will take your days off to fix.
  4. No updates when a major storm is predicted. (Winter storms could shut down our small mountain town entirely!)

A quick look at these tells me that now is not the time to upgrade. Basically, remember that Murphy’s law is always in effect, and don’t start a mess you can’t get yourself out of. I’ve been bit more times than I care to remember on what I though would be simple, quick upgrades. Fortunately I know how to get myself out of most of the messes, but there is still a cost in time and frustration. If you don’t know how to fix it yourself, don’t do it till this health crisis is over.

I’d recommend that you go through your devices and software and turn off the “Auto-Update” features so that you can be sure nothing updates without your permission. Auto updates are ok for email and web only users who don’t rely on their computers. I work on mine and down time hurts me and is frustrating. In my case, I want every update to be something I plan and initiate.

Before major updates, like system software or critical software, I always do three fresh clones of my boot drive so I can quickly “roll back” to a previous state if the update fails or is wonky. And the times I’ve need those backups, I’ve REALLY needed them.

And while I’m on the subject, don’t be the first to install new updates or new versions of software. With system software, give new versions about six months for the bugs to be worked out, and a couple months for the incremental security updates. For software like Photoshop, I give it a month or two, and I usually keep the old version installed so that I can still use it if Adobe mucks something up.

And if you’ve had an upgrade disaster happen like I have, share it in the comments so I can commiserate with you!