Tugger the SLUGger!SLUG Mailing List Archives

Re: [SLUG] today's scary thought


Nick Andrew <nick@xxxxxxxxxxxxxxx> writes:
> On Thu, Jul 15, 2010 at 04:14:38PM +1000, Daniel Pittman wrote:
>
>> Sadly, I can't right now advise a better solution than these, however,
>> since it is the main problem I face in trying to bridge two data-centers
>> and provide coherent and sensible file access.
>
> Try GlusterFS with mirroring and preference for the local filesystem.

It turns out this has a major problem, in the current iteration, for WAN use:

GlusterFS currently requires synchronous communication with all replicas for a
non-trivial number of operations, so you will pay a cross-WAN latency cost for
a whole bunch of (read-only) operations regardless — *and* have to wait for
the client to write over the WAN to the remote replica anyway.

(Also, AFR you can cause the server to consume unbounded memory and die by
 writing local data faster than the WAN can flush it, if you don't require it
 to be synchronous in writing to remote replicas.


RedHat are funding development of solid, WAN capable asynchronous replication
support, expected to land some time later this year, around the same time that
XtreemFS expect to have read/write mirroring of objects implemented.

Regards,
       Daniel

As it happens, I have just been investing non-trivial time investigating the
options available here. :)

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✣ Daniel Pittman            ✉ daniel@xxxxxxxxxxxx            ☎ +61 401 155 707
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