LTO3 and LTO4 are high speed tape drives which required a high amount of data throughput to provide adequate performance. There is a specific way to increase the caching in Backup Exec to achieve a more constant data stream to the drive buffer and keep data flowing more efficiently to the drives. Below is the default and recommendation for those settings changes within Backup Exec:
In the devices tab in Backup Exec (10-11d) right click on the tape drive.
(If there is more than one you can repeat with all tape drives) left click Properties. Click on Configuration.
This will open the drive configuration screen for backup exec. At this time you have a set of defaults. Primarily unless Symantec makes changes these will always remain the same until changed by the end user.
Block size = 64k
Buffer size = 64k
Buffer count = 10
High water count = 0
Block size This value should not be changed from the default value of 64k unless instructed by Symantec technical support.
Buffer size This value can be adjusted to either 512k or 1024k, each setting can be tested for optimum data flow
Buffer count This value can be adjusted, (with the increase in buffer size) 20 is a good start
High water count This setting is for how many of the buffers are filled before data is sent to the device. Primarily this is the most important setting as it has the responsibility of keeping the drive buffer with data. Allowing the drive to stream. A good start here is half of the buffer count, but 10-15 is always a good point of reference.
Along with these settings changes comes a noticeable delay in byte count in job monitor. This is a normal side effect due to the settings changes and the software has to cache more data.