I have several Percona Mysql databases being backed up using Xtraback. Aside from the mysqldb these are all innodb databases. These are setup on a weekly full backup schedule with multiple daily incrementals through out the week. A "fake full" or "materialized" copy is also kept. That is, as each incremental is taken it is also rolled into a separate copy of the original full for quick restoration.
On some tables it seems the materialized copy bloats throughout the week after incrementals are applied. That is to say the ibd files become very space; the du reported block size becomes nearly 2x the ls filesize. The original backed up source ibd is not sparse like this.
Has anyone familiar w/ xtrabackup seen this behaviour before? Is it expected which rebuilding backups from a full and applying incrementals? Anything to combat this?