Keeping backups
It's been a while since I described the way I do backups -- in fact, the only public document I could find on the subject was written in 2006, and things have changed a great deal since then. I believe there have been a few mentions in Dreamwidth and elsewhere, but in this calamitous year it seems prudent to do it again. Especially since I'm starting to feel mortal, and starting to think that some day one of my kids is going to have to grovel through the whole mess and try to make sense of it. (Whether they'll find anything worth keeping or even worth the trouble of looking is, of course, an open question.)
My home file server, a small Linux box called Nova, is backed up by simply copying (almost -- see below) its entire disk to an external hard drive every night. (It's done using rsync, which is efficient because it skips over everything that hasn't been changed since the last copy.) When the disk crashes (it's almost always the internal disk, because the external mirror is idle most of the time) I can (and have, several times) swap in the external drive, make it bootable, order a new drive for the mirror, and I'm done. Or, more likely, buy a new pair of drives that are twice as big for half the price, copy everthing, and archive the better of the old drives. Update it occasionally.
That's not very interesting, but it's not the whole story. I used to make incremental backups -- instead of the mirror drive being an exact copy of the main one, it's a sequence of snapshots (like Apple's Time Machine, for example). There were some problems with that, including the fact because of the way the snapshots were made (using cp -l to copy directories but leave hard links to the files that haven't changed) it takes more space than it needs to, and makes the backup disk very difficult -- not to mention slow -- to copy if it starts flaking out. There are ways of getting around those problems now, but I don't need them.
The classic solution is to keep copies offsite. But I can do better than that because I already have a web host, and I have Git. I need to back up a little.
I noticed that almost everything I was backing up fell into one of three categories:
- Files I keep under version control.
- Files (mostly large ones, like audio recordings) that never change after they've been created -- recordings of past concerts, my collection of ripped CDs, the masters for my CD, and so on. I accumulate more of them as time goes by, but most of the old ones stick around.
- Files I can reconstruct, or that are purely ephemeral -- my browser cache, build products like PDFs, executable code, downloaded install CDs, and of course entire OS, which I can re-install any time I need to in under an hour.
Git's biggest advantage for both version control and backups is that it's distributed -- each working directory has its own repository, and you can have shared repositories as well. In effect, every repository is a backup. In my case the shared repositories are in the cloud on Dreamhost, my web host. There are working trees on Nova (the file server) and on one or more laptops. A few of the more interesting ones have public copies on GitLab and/or GitHub as well. So that takes care of Group 1.
The main reason for using incremental backup or version control is so that you can go back to earlier versions of something if it gets messed up. But the files in group don't change, they just accumulate. So I put all of the files in Group 2 -- the big ones -- into the same directory tree as the Git working trees; the only difference is that they don't have an associated Git repo. I keep thinking I should set up git-annex to manage them, but it doesn't seem necessary. The workflow is very similar to the Git workflow: add something (typically on a laptop), then push it to a shared server. The Rsync commands are in a Makefile, so I don't have to remember them: I just make rsync. (Rsync doesn't copy anything that is already at the destination and hasn't changed since the previous run, and by default it ignores files on the destination that don't have corresponding source files. So I don't have to have a complete copy of my concert recordings (for example) on my laptop, just the one I just made.)
That leaves Group 3 -- the files that don't have to be backed up because they can be reconstructed from version-controlled sources. All of my working trees include a Makefile -- in most cases it's a link to MakeStuff/Makefile -- that builds and installs whatever that tree needs. Programs, web pages, songbooks, what have you. Initial setup of a new machine is done by a package called Honu (Hawaiian for the green sea turtle), which I described a little over a year ago in Sable and the turtles: laptop configuration made easy.
The end result is that "backups" are basically a side-effect of the way I normally work, with frequent small commits that are pushed almost immediately to a shared repo on Dreamhost. The workflow for large files, especially recording projects, is similar, working on my laptop and backing up with Rsync to the file server as I go along. When things are ready, they go up to the web host. Make targets push and rsync simplify the process. Going in the opposite direction, the pull-all command updates everything from the shared repos.
Your mileage may vary. Resources and references
Another fine post from The Computer Curmudgeon (also at computer-curmudgeon.com).
Donation buttons in profile.
[Crossposted from mdlbear.dreamwidth.org, where it has
comments. You can comment here, or there with openID, but wouldn't you really rather be on Dreamwidth?]