Re: [Gluster-devel] AFR between two bricks over 3000 miles

[nathan]

On Thu, 3 Apr 2008, Krishna Srinivas wrote:

> >  Thanks! So is the ability to have two sites that are over 500 miles apart
> > planed to be supported? I will test out the new code and let you know.
>
> Hi Nathan,
> It is already supported but is slow as of now because of the slow link :)
> But to make it fast over the slow link will be complicated, we have
> not yet clearly
> thought about how it can be achieved.

That is just it, it is NOT a slow link. It is a full gig E between NYC and 
SJC. The issue is all the back and forth transactions. It does not matter 
if it is a T1 or a GIG E your only going to get about 100k miles a sec. So 
a request and then reply is going to be about 65 ms.

This is why people hack TCP/IP for sat links, you can have a full 
transponder to use, but you send your 1500 byte packet, 250 ms from earth 
to the sat back to earth and then the ack back another 250 ms. So you have 
this big pipe but you can't use it most of the time because of the delay.

Since gluster can use a number of flows at one time, you should be able to 
come close to maxing a gig e from east to west, but right now you can't 
even get close.

-Nathan