Backup size more than twice bucket size?

While validating cbbackupmgr (v4.6.2) it is noted that the size if the backup is more than twice the size of the bucket. Is that normal? If so, how can it be explained?

Here is the backup size:

# /opt/couchbase/bin/cbbackupmgr list -a /var/mf/cbbackup/bfx_archive/
 Size      Items          Name
 59.95GB   -              /
 59.95GB   -              + bfx_archive
 59.95GB   -                  + 2017-06-23T09_36_36.520011134+02_00
 59.95GB   -                      + sjoerd
 331B      0                          bucket-config.json
 59.95GB   150000000                  + data
 59.95GB   150000000                      shard_0.fdb
 2B        0                          full-text.json
 4B        0                          gsi.json
 2B        0                          views.json

So, this lists 60GB roughly.

Here is the screencap, showing an actual bucket size of 25.3 GB.

This is a known issue with cbbackupmgr and we currently have improvements scheduled to be released in 5.0 to reduce the size (–value-compression flag). One thing you can do in the meantime is to run the cbbackupmgr compact command. This will help to reclaim fragmentation in the file.