[ZODB-Dev] Clustering ZEO Server with drbd

[Jens Vagelpohl]

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On 29 May 2006, at 16:45, Christian Theune wrote:

> garthpl at periweb.com wrote:
>> Hi folks, I'm looking at making a scalable zope infrastructure, I  
>> can scale the ZEO clients and mysql, the only issue is the ZEO  
>> server. I have used drbd and heartbeat in the past to create a HA  
>> lamp stack. From a technical standpoint, is there any reason I  
>> could not use drbd to cluster the ZEO server? Any thoughts would  
>> be appreciated.
>
> As far as I understand, the difference to ZRS (which is a solution  
> to scale ZEO servers, e.g. for HA) that you will need to restart  
> the ZEO server when switching a hot-spare ZEO server to "live- 
> mode", because it doesn't notice when the underlying storage file  
> is changed by somebody else.

The hot spare ZEO server in a ZRS setup is read-only. ZEO clients  
will be glad to switch to it automatically (this is a built-in ZEO  
feature, you can specify more than one server and the clients will  
hunt for another one if the first one goes down), but if you want to  
make the hot standby read/write you have to restart it.

jens


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