Speed problem

uwp at dicke-aersche.de uwp at dicke-aersche.de
Tue Nov 12 00:06:00 EST 2002

On Mon, 11 Nov 2002 jw schultz wrote:

> You haven't really provided enough data to even guess what
> is limiting your performance.

As I said in the last mail: One limit for sure is ssh.
But: with arcfour I'm getting 18 MB/s and that's where
rsync is actually starting. It's just getting down and
down and that's the strange point.

> You need look at CPU utilization, I/O load and network load

The CPU is at 100% for encryption reasons of ssh. But I/O
is not very much.

> Is the 18MB/s actual data transfer (just what has changed)
> during actual transfer?  If so you may be up against the
> limitation of your disk+file systems.

The disks have an upper limit of 52 MB/s (ext2) respectively
45 MB/s (ext3). It's an IDE RAID with 12 WD disks.

> My gut reaction is that 18MB/s is probably just short of the
> best sustained throughput you can get out of your disk

Nope. The average of the disks over a long period is between
31 and 38 MB/s. I tested it without ssh.

Just to say it again: I wouldn't have a problem with 18 MB/s,
that's what I expected. I just have a problem with the fact
that it goes down to 400 KB/s in half an hour...:-(

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