Re: writing pseudo-random data to disks

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

Hello,

yudi v a écrit :
> I am using the below command/s to write to 3TB hitachi deskstar 7200RPM
> disks.
> 
> dcfldd if=/dev/urandom status=off | PV -s 3000G | dcfldd of=/dev/sda
> of=/dev/sda of=/dev/sdb status=off bs=4096
> 
> on the HP microserver nl40 with SATA 3Gbps connection, the throughput was
> 3-4MB/s, around 10.5 days.
> Where as on my desktop with i5 CPU and 6Gbps connection, the throughput is
> 13-14MB/s, around 61 hours.
> 
> My question is: where is the bottleneck on the HP for such low throughput?

The bottleneck is /dev/urandom, i.e. the CPU. Any recent SATA disk
should sustain at least 50 MB/s throughput.