Compress SQL Backup Files
Here’s a nice little utility that compresses the SQL backup files .bak using Gzip. The backups will then take up a lot less disk space.
forfiles /P G:\SQLBackup\db /S /M *.bak /c "cmd /c if @isdir==FALSE C:\GZip\bin\gzip.exe @path"
Add that as a SQL Agent job and call it after the database backup in the maintenance plan.