LevelDB can become corrupted when bad things happen on the filesystem or in hardware. We push the I/O to the limits on heavily loaded Riak nodes so it is not uncommon to experience such failures. This one exhibits as a message Compaction error: Corruption: corrupted compressed block contents in the «data_root»/leveldb/«vnode»/LOG
file.
[root@prod-2163 /var/db/riak/leveldb]# find . -name "LOG" -exec grep -l 'Compaction error' {} \;
./442446784738847563128068650529343492278651453440/LOG