Dealing with a very large file -1,5TB

[Christoph Klocker <cklocker@xxxxxx>]

Hi

I am developing a system to stream very large uncompressed videofiles 
which are about 1,5TB.
I need a bandwith of 195MB/s.
my system is now:
kernel: 2.4.18
xeon 2,4GHz
1GB RAM
3ware escalade controller 12 s-ata harddisks, seagate barracuda 7200.7 - 
120GB - SCSI

when I do different tests with bonnie++ I get very good results for a 
2GB file, readperformance 249mb/s,
but when the files get larger the speed is going down significantly.
at 10GB - 216MB/s
at 100GB - 187MB/s
at 1TB - 161MB/s
the write performance stays at 183MB/s any time, up to 1TB.
As my harddisk have a sustained rate of 32-50 MB/s it should not be the 
case that they influence the results.
I am now thinking maybe the filesystem influences the result when the 
disks are getting fuller. I thought also about that the logfiles get 
bigger and bigger and that maybe a reason.

I had a look if its possible to switch of the logging completely (there 
is no reason to have it because I just have one file) , but I think its 
not possible with xfs.

Is there a special parameter configuration for having just one file at 
this size (1,5TB)

/Christoph

_____________
Klocker Christoph
KTH-AMT
10044 Stockholm