It turns out that there was a bug with the Amanda S3 device: it had issues with buckets that had a lot of keys (files) in it. Due to the way Amanda works it makes one gig pieces of data on the holding disk and then the S3 device chunks them up smaller and puts them on the S3 device. When the tape/bucket was due to be resused the files in it had to be removed. Fetching the key list (file list) that could be rm’d had a buffer overflow.

I found this out with the awesome help of djmitche (and Freenode #amanda) who wrote a patch for me. I’m pretty sure the patch made its way into amanda trunk. In Gentoo the patch is in app-backup/amanda-2.6.0_p2-r1.

Since applying the patch I’ve had no problems with Amanda at all and it’s run perfectly for me.

I’ve been having issues with both Amanda+S3 as well as JungleDisk. I’ll outline these here.

JungleDisk Problems

• JungleDisk sometimes destroys all of my data on S3 in the bucket JungleDisk uses and then on the next backup re-uploads all of the data! This is clearly a problem. Luckily I do not have more than a gigabyte of data thats backed up with JungleDisk. If I did this bug (or feature?) would be very expensive.
• JungleDisk doesn’t smartly handle moves. I’d like to be able to move things around on my local filesystem and have JungleDisk notice this and move them. Moving them over WebDAV isn’t feasible.
• JungleDisk scans individual files and doesn’t combine a whole bunch of them into one tarball. This gets very expensive! I wish they’d tar it all up first like Amanda.

Amanda+S3 Problems

• Sometimes the Amanda S3 device module has problems talking to S3. The only fix I’ve found so far is to destroy the bucket, remove it from the tapelist, readd the bucket, reidentify the bucket to Amanda and run amflush. This is clearly not good as it’s just as bad as Jungledisk destroying everything. I haven’t figured out why this happens yet.

Both products are still good and I’ll continue to use them. I’m considering using Amanda on my laptop, however, but this could cause problems in cases where it isn’t connected to the network at backup time.

Seeing how well it worked for her I asked her to show me how it worked and now my server is also using Amanda to backup to S3. Recovery works with amrecover.

I have quite a bit of data to back up (4.5GB in /home, for example) and with a home DSL connection it takes a long time. However with a bigger pipe using S3 and Amanda would be extremely viable.

I’m very happy with the solution and will likely use it across all of my servers from now on.

For my laptop I’m still using JungleDisk, which seems to work fine. 2.0 is a very good improvement.