I've finished compressing the autoburt snapshots.  This has reduced the space utilization on /ligo from a high of 81% down to 48%.  The rough compression ratio was about 10:1.  In each burt year directory with compressed archives there is now a CHECKSUMS.MD5 file with the md5 checksum of each archive which may be used to verify the integrity of the archive if needed.  Rsync backups of /ligo should now be somewhat more efficient as well with fewer files to compare looking for changes.