Musings on Photography

Offsite Backups

Posted in equipment, file storage, hardware by Paul Butzi on January 10, 2008

The photo above is the Mac Mini based fileserver described in this post. The square white thing under the disk drive to the right is a bit of styrofoam packing material I stuck under the disk drive because the vibrations of the disk drive were making the countertop resonate and filling the room with a loud hum. The big off-white thing to the left is a UPS (uninterruptible power supply) that can run the server for about fifty minutes from the battery. (I could probably have gotten by with a smaller UPS; it only has to keep the server alive for the 30 seconds before our backup generator kicks in. If the power is out for more than about 40 seconds it means the generator failed to start, so the server is actually configured to shut down gracefully after three minutes on battery.)

Several folks have asked what I do for offsite backups. Since I just ordered new gear to revise my offsite backup scheme and make it easier to keep up, I’ll detail the new scheme.

What I bought were two one terabyte Western Digital MyBook external disk drives. Western Digital offers a confusing array of Mybook models which vary in case color, shape of the status lights, and a minor change in case dimension, all of which are of little importance to me. They also differ in the format of the filesystem the disk ships with; I always reformat a disk before using it (after reading about disk drives shipping from factories pre-infected with viruses), so that part doesn’t matter to me either. And finally, the important variation – the variety of interfaces the external disk can support. Nearly every combination of USB 2.0, Firewire (aka IEEE 1394a), Firewire 800 (aka IEEE 1394b), and eSata is offered. In general I choose the disk model with the largest number of interface options, to preserve my choices into the future. This most recent purchase, though, I bought the MyBook Home Edition, which gives me USB 2.0, Firewire 400, and eSata, but not Firewire 800. That’s because a) the Mac Mini doesn’t have Firewire 800, and b) I was able to exploit a price break.

So here’s my basic plan:

  1. To start, I copy everything onto one of these disk drives. I then give this disk to my friend Bryan, who generously stores it in his house.
  2. Then, once a month or so, I take the disk I still have, copy everything onto it, and exchange it for the one at Bryan’s house. The new disk goes back to Bryan’s place, and the one that had been at Bryan’s comes home, to be used the next time around.

This way, if some calamity results in the loss of every copy of data stored on the redundant servers at my home, I can go, get the disk from Bryan, copy it off that (now very precious) disk, and I’m up and running without any data loss. What sort of calamity might cause me to lose everything? The two big risks are probably a fire (my home was threatened by a forest fire just a few days after we moved in), or a burglary where the burglars are very thorough and make off with ALL the disks that comprise my redundant system of servers and workstations.

You can reduce the risk even further, by having multiple offsite copies. You don’t need to add two disks for every offsite copy. If you want N offsite copies, you’re fine with N+1 disks; you stagger the replacement and so you only need one extra disk beyond the disks stored offsite.

Finally, the reason why I don’t have one disk for each offsite backup, and go and get the disk, write a fresh backup onto it, and then replace it offsite – that’s because I know that what will happen is I’ll retrieve the disk, then it will sit around for a while before I remember to write a fresh copy, and then more time will elapse before I remember to put it back at the offsite location. In the end, if I do this, the offsite disk is actually offsite a small fraction of the time – and thus doesn’t offer any increased protection.

I’ve looked into doing offsite backup on a offsite server, transferring the data via my internet connection. Since I pay for the bandwidth I use, this ends up being an expensive option for me.

A final note: in the past, my offsite backups were written by the FreeBSD server, and thus used the native filesystem for FreeBSD. This caused me some anxiety (I can’t read those disks on any other of my computers) and some moderate amount of hassle. In the future the offsite backups will be written by the Mac Mini, and will be in the Mac native filesystem (HFS+) so that I can just plug the disk into any Mac and get at the data. This is one more reason for shifting away from the FreeBSD server. And although in theory you can plug a USB disk into the ReadyNAS NV+ and write a backup to it, I’ve never been able to get that to work. Beyond the fact that I had the keyboard, mouse, and monitor, it’s another reason why the Mac Mini based server system isn’t headless – having a keyboard, screen, and mouse makes it easy to do things like write the offsite backups when needed.

2 Responses

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  1. latoga said, on January 19, 2008 at 11:35 am

    Paul, Have you ever looked at any of the online backup options that are now available on the market?

    They work in the background, uploading your files to a huge online storage system. Obviously you need to have your computer on quite often and a broadband internet connection to use them, but once you install it and configure it you just forget about it. My previous employer used these to backup our laptops, but I haven’t thought about it for my photography.

    I can see it would save you the hassle of remembering to swap drives every month.

  2. Paul Butzi said, on January 19, 2008 at 11:52 am

    Paul, Have you ever looked at any of the online backup options that are now available on the market?


    I have a very fast internet connection, so speed isn’t the issue. The hitch, for me, is that my connection is not flat rate: above a certain amount of data transferred, I have to pay some rate (I think it’s currently $5/GB) to transfer the data.

    In other words, using a networked online backup system would cost me $5/GB of backed up data, above and beyond the cost for the service. The marginal cost for disk right now is about $0.30/GB – even when I double that for the two disks to rotate offsite backups, it’s still a factor of 8 difference.

    For someone who pays a flat rate regardless of how much data they move, such services do look like an appealing option, presuming that you trust the service you have backing up your data. If I were looking to use such a service I would be encrypting the data before transmitting it to the service.

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