Fast Compression parameter may be set to force a full backup every 7 days or if the threshold reaches 20%. However, a full backup may be generated every day and not following the parameter settings in the Fast Comp maintenance plan.
There maybe another process, non-litespeed backups, performing a backup operation which may cause Litespeed fast compression to re-init it's full backups.
You may see something similar in the log, indicating there's another backup process that exists:
Initializing new FastCompression-managed backup sequence
Selecting full backup: Last full backup is not a valid LiteSpeed backup located in a FastCompression-managed folder
Executing SQLLitespeedx64.exe: Write new full backup to 'C:\Backups\SQL\User\OTHERBACKUP.litespeed.f3.bkp'
Stop the other backup process.
If another application is moving or deleting the Full backup file (like moving the file to tape) before LiteSpeed FastCompression runs again, it will run another Full.
By adding Reporting & Logging to the FastComp MP, a text file is generated that includes the message below. If you add the Notification, you get the same info via email. It explains why the program chose to do a Full, rather than a Differential backup. I
"Initializing new FastCompression-managed backup sequence
Selecting full backup: Last full backup is not a FastCompression backup located in managed folders
Executing SQLLitespeedx32.exe: Write new full backup D:\Backup\2005\pubs.litespeed.f0.bkp"
