Backupexec with HP MSL 2024

Hi All

      I have HP Backup Libraries MSL-2024 Backup tape , i need backup 4 server , all is windows 2003 and 2000, but in frist day buy to this one , the backup job need over 1 day backup the data ?? the performance so poor ????  backup local server use about 1800MB/min , but backup other server use about 800MB/min , so the driver need about 27hours backup all data !!!! help ,, this is setting problem or this is normal for the software

??? i set the configuration (Block size 64K, Buffer size 64K, Buffer count 10 ) , and other setting improve the performance , Thanks,