Avoid snapshot as a backup tool. The best way is take a snapshot before your maintenance and delete after confirm that's all ok. VMs that has many modifications as write database, could have a delta file bigger and decrease performance. Take a look on vSphere Data Protector appliance for backup.
Emanuel Álamo
NCDA+MCSA+MCSE+VCA-DCV
VCP-DCV+VCAP-DCA+VSP+VTSP
VMware Mobility