[Infrastructures] Coda, to do or not to do?

[Ivan Popov]

On Fri, Mar 18, 2005 at 09:03:13AM +1300, Steve Wray wrote:
> Everything was great until I tried to play a 700M avi file on the client 
> at which point the server would (very reliably) crash.
> 
> Playing a 400M file was no problem.

> thinking now that it this client-cache-filling-crashing-server came up
> in private emails with Jan Harkes (the lead developer at the time IIRC).

> I'll see if I can fish any of that out of my personal email archive.

I think it would be good to find out what you really meant,
otherwise the fellow guys on this list might get confused :)

> Anyhow, its *easy* to test
> :)
> just be prepared for the server going down...

Ok, testing! Taking the risk :-)
Installing a playground client to imitate your conditions.
Creating a 700M file with "dd if=/dev/zero bs=1048576 count=700 of=700M".

-------------------------------------------------------
# sh coda-client-setup 500000
 ...
*** Going to install about 7 Mb software and let Venus have 500000 Kb cache.
 ...
[logging in as an ordinary user, authenticating against a Coda realm]
 ...
$ cd /coda/ejo.realm/uzant/eta/tmp
$ pwd
/coda/ejo.realm/uzant/eta/tmp
$ ls -s 700M
1433600 700M
$ wc 700M
wc: 700M: No space left on device        [which is of course expected]
                                         [no fetching happens at all]
                                         [there is still 500M free in cache]
$ cfs cs
Contacting servers .....
All servers up
$
-------------------------------------------------------

I would be really excited if it broke - as it is a thing many novice users
are curious about... And some of them test, of course :)

You can not read a file bigger that the actual client cache,
it is a fundamental property, ensuring we can access cached files
even while disconnected.

Of course, I can access that file on another client (e.g. my usual
workstation where I am writing this letter has 6G Coda cache)...

> it just seems that these days AFS is a more mature solution to the same 
> problem...

Not really :-)
AFS and Coda do not solve the same problems.

In contrast to AFS Coda supports disconnected mode, write replication,
provides a global name space, does not need realm-dependent client
configuration, a Coda realm can use services of different authentication
databases, which do not have to be just Kerberos.

Neither of those is possible with AFS.

AFS is mature and good, but Coda and AFS despite common roots
have their own and different areas of suitability.

Best regards,
--
Ivan