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Date: Tue, 17 May 2011 13:53:57 -0700
From: Maxim Sobolev <sobomax@FreeBSD.org>
Organization: Sippy Software, Inc.
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Subject: Making hastd working over WAN links (was: Randomization in hastd(8)
 synchronization thread)
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On 5/17/2011 1:28 PM, Maxim Sobolev wrote:
> The next thing to make it usable is to make "async" mode working. I
> think simple support for that mode can be easily implemented by not
> sending write request to the remote note at all, but instead just doing
> it locally and kicking the synchronization thread to do it's magic in
> the background. I hope to follow up with the patch soon.

Here is a proof of concept path, which simply fails any 
non-synchronization requests in the send thread when in the async mode. 
This is non-optimal, as it would cause additional latency in the write 
path when the send thread is busy with synchronization requests. But it 
works for me, making it possible to use my virtual machine while 
synchronizing the disk image.

http://sobomax.sippysoft.com/primary.c.diff

-Maxim