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From: | Daniel Maher |
Subject: | Re: [Gluster-devel] Architecture advice |
Date: | Mon, 12 Jan 2009 14:32:09 +0100 |
User-agent: | Thunderbird 2.0.0.19 (X11/20090105) |
Gordan Bobic wrote:
How does the HA translator choose a node, exactly ? Does it randomly select one from the list of available subvolumes, or does it pick them in the order they're specified in the config file, or some other way entirely ?Not sure what the default is, but you can specify a preferred read server (writes have to go to all servers regardless) with"option read-subvolume" in the volume spec.
option read-subvolume is available only in the AFR translator, and if AFR is being done on server-side (the scenario noted previously in this thread), then there would be no AFR declaration in the client spec file, and thus no way to set the read-subvolume option.
The HA translator is not that useful in the context of a straightforward client-side AFR setup in any case, since (as i understand it) if a given server dies, the client continues to interact with the remaining defined servers seamlessly. This, of course, is part of the attraction of defining AFR on the cleint side ; but in cases where it is not feasible (overhead concerns, etc...), using HA with server-side AFR is a very interesting prospect.
Some way to extend simplistic load-balancing features to the HA translator (or, perhaps, another translator working in concert) would therefore be quite ideal.
-- Daniel Maher <dma+gluster AT witbe DOT net>
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