In my last blog posting, I described the events that have lead up to my paranoia about keeping my computer backed up. In this posting I'll talk about about how I actually keep my system backed up and the challenges involved in these methods.
These backup strategies are appropriate for individuals and for small offices. For larger environments, the reasons for doing various types of backups still hold true, but the implementation strategy will change significantly.
1. DVD Backup. My first strategy is mundane - my software development directories are backed up to DVD after every release. This is more complicated than it sounds. First, Visual Studio creates hundreds of megabytes of temporary files, including .ncb, .ilk, obj, and .pch files. There generally no point in backing up these files. In Roxio Creator I can exclude all of these file types, which makes it trivial to just drag the root directory of my development structure to the DVD. Other DVD burning applications, such as CDBurnerXP, won't automatically exclude file types, so it's somewhat more complex to use them for backups. [Update 12/21/2010: CDBurnerXP now supports excluding by extension, under Edit/Filter Files. However, you can't use this filter from the command line.]
I've been careful to use high quality CDs and DVDs for these backups. I have CDs I burned over ten years ago that I can still read without difficulty. My recordable DVDs are newer, so the jury is still out on how long they'll last. The important thing to remember about CD-R and DVD-R is that, unless you buy archive-grade media, they shouldn't be expected to last more than a few years.
DVD and CD backup requires a substantial amount of effort. You have to remember to do it, it's relatively time consumering (especially if you validate the media after burning), and you have to keep all of the media labeled and filed. So it's only a good streategy if you are quite disciplined. However, DVD backups are much easier to move offsite and you have a permanent record, especially if you need an audit trail.
2. Image Backup. Image backups are the cornerstone of my backup strategy. If my computer total fails, due to a virus, a lightning strike, or user error, the image backups are what allow me to recover in a few hours instead of a few days.
For the last eight years I've created my image backups with Acronis TrueImage. This has been a mixed blessing. On the plus side, Acronis can do incremental image backups, which saves a lot of disk space. Acronis has a standalone boot CD, so you can recover the system from a raw hard drive. Acronis can do backups over the network, even when booted from the recovery disk. All of these have been invaluable.
On the minus side, Acronis has had significant difficulty with consistent quality. Their latest release, Version 11, is a total disaster and has been completely unusable for many people. Acronis also has a nasty habit of creating corrupted backups, which means that a validation phase is required.
I do image backups once a week, supplemented by file backups that are done daily. I try to keep three months of image backups because some viruses can take weeks to trigger.
[Update 12/21/2010: Because of ongoing stability problems with Acronis, I have stopped using it.]
3. File Backup. Acronis TrueImage can also do file backups. I backup my development directories and documents on a daily basis. This usually comes out to less than 5-GB, so I can store a lot of them on a 1-TB backup disk. Again, file backups are done incrementally, so the baseline file is dramatically larger than the daily incremental files.
My big problem with Acronis is the poor support for rotation management. I want to keep backup snapshots every 30 days for the last six months, every week for the past month, and every day for the past week. Acronis provides several different options, none of which can do what I want, and all of which seem to cause the frequency of corrupted backups to increase dramatically. [Update 12/21/2010: Macrium Reflect also has better support for managing archive rotation.]
File backups provide protection from accidental deletion and provide the ability to revert to an older version of a document.
4. RAID 1 Mirror drives I mentioned this in my last blog post, but it bears repeating. I use mirrored drives to handle the case of catastrophic hard drive failure, which has happened to me multiple times before. One of the two mirrored hard drives can fail completely and it won't affect the performance of the system. [Update 5/30/2010 - This happened to me again today. A hard drive failed in my primary development system. Without the RAID 1 pair I'd be looking at restoring from backup right now.]
I use software RAID (Intel Matrix Storage), which definitely has its downsides. Every time you reboot without cleanly shutting down the system, (such as a power fialure or hitting the Reset button,) the drive mirrors have to be validated. This takes six to ten hours, during which the system is almost unusable.
Hardware RAID solutions with battery backup can fix this problem, but such RAID hardware is dramatically more expensive and generally is not compatible with image backup software such as Acronis.
Note that not all RAID strategies provides protection. RAID 0 (striping) actually DECREASES reliability, because if any drive fails, your data will be completely lost.
5. Online backup. My final strategy is for last ditch disaster recovery - theft, fire, natural disaster. I'll talk about it in the third and final part of my blogs about backup.