Now, logfiles tend to be compressible, so in preparation for migrating it to a new host (it's a zone, so moving from one physical host to another is trivial) I tested ZFS compression to see how well that would work.
Now, the default lzjb gives you fair compression. That saves 80% of my storage, so that's pretty good.
Going to gzip compression the space saving is spectacular. Unfortunately the machine runs like it's stuck in treacle, so that's not exactly practical.
Which is why I tried gzip-1. You save much more space than lzjb, although not as much as the default gzip (which is gzip-6). Unfortunately, while the machine doesn't quite go as comatose as it does with the regular gzip compression, the performance impact is still noticeable.
Overall, while I wouldn't mind the extra compression, the performance impact makes it hard, so I'm going to stick with the regular lzjb.