performance problem with partition with 47 GB of data

[FM]

Hello,
We have performance problem with a 47 GB partition (on the backup server).
OS : Linux Redhat Enterprise AS 3 V4
Version : amanda-2.4.4p1
/dev/cciss/c1d0p2     160G   56G   97G  37% /amanda
inparallel 50
netusage  30000
maxdumps 5
holdingdisk hd1 {
    comment "main holding disk"
    directory "/amanda/daily"
    use -50 Mb
    chunksize 4 Gb
(...)
}
Can force the backup order so this partition is the first one to be backup ?
Expect for inparallel and maxdumps, is there other parameters that can 
increase my backup perf ?

thanks !