Coda File System

replication

From: Patrick Walsh <pwalsh_at_esoft.com>
Date: Fri, 27 May 2005 11:00:04 -0600
	(I'm still waiting for more help on the problem of venus crashing with
signal 11's, but in the meantime, I have some more general questions).

	I'm writing tests to make sure coda handles various disconnected and
failure states well.  One test simulates this scenario:


,_______.         ,_______.       ,_______.        ,________.
|Clnt 1 | <----> | Svr A | <---> | Svr B | <----> | Clnt 2 |
`-------'         `-------'       `-------'        `--------'

(in case that doesn't come through somewhere, I describe it below)

	Client 1 can see Server A, Client 2 can see Server B and the two
servers can see each other.  Given a replicated volume, R, my
understanding is that, in strongly connected mode, if Client 1 writes a
file to R then Server A passes that file on to Server B before returning
from the store call.  Correct?

	If that's the case, then Client 2 should be able to see the new file
fairly quickly, right?  Alas, in my tests, it takes between 5 and 10
minutes before Client 2 can see the change, regardless of how many times
I try to flush the cache, checkservers or checkvolumes.

	Note: both clients know about both servers even though they can't see
them.

	What causes this to be slow?  How can it be made faster?  Is it
intended behavior?

	Thanks.  And expect more questions of this nature as I dig farther into
my tests.  I'll document any new conclusions, of course.

-- 
Patrick Walsh
eSoft Incorporated
303.444.1600 x3350
http://www.esoft.com/

Received on 2005-05-27 13:01:03