Backup Speed

Hello,

            We have been having issues with backup speeds to backup-to-disk folders. Our current speeds to our folder have been around 400MB/min. The folder is located on a local partitioned drive. We are using advanced file option however this is what we use when we backup to our LTO device which is connected via SCSI. The speeds were getting when we backup up to the device average 800MB/min.The backup to the folder initially starts around 1200MB/min but after 5 mins drops to about 400. I would think that the speeds to a local drive would be faster then backing up to a device. I increased the maximum size for backup-to-disk files and I selected allocate the maximum size. I also selected software type for compression.  Is there anything that I could do to increase speed?