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Re: [Gluster-devel] Glusterfs HA & AFR


From: Daniel Maher
Subject: Re: [Gluster-devel] Glusterfs HA & AFR
Date: Wed, 18 Feb 2009 10:40:40 +0100
User-agent: Thunderbird 2.0.0.19 (X11/20090105)

Chris Mavin wrote:

Can someone clarify the following for me.
I'm using Glusterfs RC 2. If I am using the HA translator rather than AFR, Does this expect to be using a shared storage accessible from both servers? Put another way, is the HA translator simply a way of providing High availability for a SAN? When I test it using 2 servers the active server is written to fine but the backup server simply gets a 0 byte file written to it.

HA is, afaik, just a way to switch communications between target machines - it does not itself have any sort of replication features, nor does it have the ability to speak to multiple targets simultaneously.

Given three machines :
- ClientA
- ServerA
- ServerB

If ClientA is configured to communicate to ServerA & ServerB via HA, it will pick one (ServerA, for example), and speak to it exclusively until such a time as ServerA stops working - whereupon it will communicate with ServerB.

Nowhere in that scenario is data replicated or copied between ServerA and ServerB. For this, you'd either need to set up server-side AFR between ServerA and ServerB (and keep HA on ClientA), or set up client-sde AFR on ClientA (and ditch HA altogether).

--
Daniel Maher <dma+gluster AT witbe DOT net>




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