RSH scaling problems...

Trent Piepho xyzzy at
Tue Dec 24 18:47:05 PST 2002

On Thu, 19 Dec 2002, Robert G. Brown wrote:
> you've got wirespeed limitations of perhaps 100-100 MB/sec, and disk
> speed limitations that are likely less than that.  So the speed penalty
> is 2-3 in total speed for using ssh to transfer huge files.  This isn't
> particularly terrible for most file transfer applications, unless all
> you are doing all of the time is file transfer and it is significantly
> rate-limiting.  

The test system here was a 2.4 GHz P4 with a 40MB IDE drive.  That's pretty
low on the ratio of disk speed to CPU speed.  We have 1GHz P3 with a 3ware
7850 card, probably has 1/3 the CPU speed and 5 times the disk bandwidth.
In this case ssh vs rsh speed is more like a factor of 10.

> So although I love ssh relative to rsh and strongly advocate its use, it
> isn't perfect and these three things, in particular: a "none" cipher

It's even more annoying that these features were would be easy to add or even
used to exist and were removed.  It's just the fascism of the openssh team
that keeps them out.

> hack these features into the linux "portability goop" (their term for
> the OS-specific layer on top of the universally shared operational
> core), but I suspect not, or at least not easily.  The cipher almost
> certainly not, and quite possibly not the disconnect either.

What's really needed is for someone, like say Redhat, to maintain a set of
patches to ssh to add features that the ssh people don't like.

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