Coda File System

Re: replicated servers

From: Patrick Walsh <>
Date: Fri, 08 Apr 2005 08:42:01 -0600
On Fri, 2005-04-08 at 10:30 -0400, Greg Troxel wrote:
>   The second realm thing was because there's no dns
>   setup on my test boxes and without that realms entry I have to use the
>   ip address to access the replica 
> I don't follow this at all.   realm is a name for an SCM. 

	Actually, I believe a realm is a name for a collection of servers.
From a client's standpoint, it doesn't matter which one is the scm or if
an scm is even available.

> record, that's used.  If not, name (or IP I guess) is used as SCM.  

	Right, that's how it should work.  But if the name can't be looked up
in dns, it fails.  It only checks the /etc/hosts file (as far as I can
tell) when a machine name is referenced in a realm definition. 

> are you trying to set up a new realm with a replicated server, or add
> a replicated server to your existing realm?

	I'm adding a replicating server to my existing realm.

> failing if mismatches from server's idea of realm.  You don't, I
> think, access servers directly, but SCMs.

	Again, from the client's perspective, it shouldn't matter if it's
talking to an scm or not.  At least, that's my understanding.

> 	  *** My original question is: do I have to do any sort of volume
>   creation on the scm or the replica to get that replica to host certain
>   volumes?  A volutil command or a config file edit?
> You have to create a replicated volume on the SCM, and then
> I think instantiate it on the two servers, one of which may be on the
> same machine as the scm.   I'm not up to speed on this.
> see sbin/createvol_rep

	createvol_rep fails if the volume already exists on the scm.  The
documentation is outdated and makes references to updating the VSGDB
file, which is no longer used.

> 	  *** My secondary question: how do I test to see if the replica really
>   has copies of the scm's files?  (I plan on disconnecting the scm,
>   flushing the cash on the client and testing that way, but I'm hoping
>   there's an easier way.)
> That's what you want to actually work, so yes, do that.

	I'm sure there must be another way.  Otherwise how could you test your
servers in a live environment.  If you take down the scm and it turns
out your replica didn't have the files, then you just disconnected all
your clients.

> You may want to have multiple scms and multiple servers, so you can

	One scm is plenty.  

Patrick Walsh
eSoft Incorporated
303.444.1600 x3350

Received on 2005-04-08 10:43:40