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Date: Wed, 4 May 2011 10:02:37 -0700
Message-ID: <BANLkTi=4qq7efiegZQujj3N3y7Xc25bmNA@mail.gmail.com>
Subject: Re: Importance of latency in a global deployment
From: Mahadev Konar <mahadev@apache.org>
To: user@zookeeper.apache.org
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Camille,
 Am glad to see a ZK deployment across Data Centers in prod. Would you
be able to write a small FAQ/wiki on
https://cwiki.apache.org/confluence/display/ZOOKEEPER/Index

For a cross colo deployment? A small write up on the challenges you
faced and how to resolve them and your configuration settings and why
you chose those?

This would be very very handy for folks thinking abt ZK cross data centers.

On Wed, May 4, 2011 at 9:55 AM, Fournier, Camille F. [Tech]
<Camille.Fournier@gs.com> wrote:
> Global clusters will affect writes greatly, and may also affect you clien=
t reads in an indirect manner.
> Writes, having to traverse from one region to another for purposes of vot=
ing, will be slowed down considerably by the ping time between regions.
> If you did a three node deployment in the manner you mentioned, your clie=
nts may also suffer. Usually you would want to have a list of all available=
 cluster members for your client to connect to, so if one is down or goes d=
own the client can fail over to a running node. However, given that your cl=
ient will have regional affinity for at most one of your servers, if you us=
e the standard zk client connection logic your client either may be connect=
ed to a far region (slowing down all responses due to latency) or the clien=
t would have no failover node available should their close region node fail=
. If you choose to have clients able to connect to any node you may also ha=
ve wan traffic considerations.
>
> Some of the client side issues may be alleviated by using observers.
>
> I've got deployments across regions to handle data center failure, but in=
 all cases the off-region member is not available for client connections, a=
nd is kept from acting as leader to prevent slowness on writes.
>
> C
>
> ----- Original Message -----
> From: Oliver Wulff <ownaish@gmail.com>
> To: user@zookeeper.apache.org <user@zookeeper.apache.org>
> Sent: Wed May 04 12:37:43 2011
> Subject: Importance of latency in a global deployment
>
> Hi there
>
> I'm quite new to the zookeeper project and got a question regarding
> robustness of the failover functionality in a global deployment.
>
> Are there any pre-conditions how close the zookeeper servers must be to e=
ach
> other from a geographical distance point of view?
> The reason is that the servers have to monitor and sync with each other i=
n
> realtime and the latency might play an important role if for instance one
> server is in the US, one in Europe and one in China.
>
> Thanks
> Oli
>


--=20
thanks
mahadev
@mahadevkonar