Investigate couchdb disk space usage

on urchin, the shards have 2.9gb, but the backup only 1mb.

root@urchin:~# du -sch /opt/bigcouch/var/lib/shards
2.9G	/opt/bigcouch/var/lib/shards
2.9G	total
root@urchin:~# du -sch /var/backups/couchdb
972K	/var/backups/couchdb
972K	total

maybe it's all old revisions that can get reduced, i didn't have the time to dig further. maybe the backup isn't working as it should.

(from redmine: created on 2013-12-14, closed on 2014-01-28, relates #4759, relates #4778 (closed), relates #4795, relates #6725 (closed))