Hi. Is it possible for ZEO to be configured with multiple databases, one for each virtual host similar to creating a ZODB mount point for an instance so if there is a problem with a site's database it is limited to a single site and that individual backups can be made of each ZODB? Many thanks. Regards, David

Hi Dieter! This is really nice to know. Zope is really flexible and so awesome as a result. If I wanted to configure with multiple zodb for a single ZEO server you say there may be a possible downside in requiring a single ZEO server per database instance further down the road. Is this something that is currently planned so I don't implement something that will not be supported later? It could be also be a bit of a problem since each ZEO server requires its own RAM. RAM is a valuable commodity. My goal is to ensure that customers I work with are working exclusively in their own zodb. It seems preferable for these zodb's to be associated with a single ZEO server (instead of each zodb mounted in a single zope instance) to make maintenance tasks smooth and handled asynchronously. Would you agree? I realize that if resources were unlimited, it would be best for a single ZEO server to use a single zodb and have one or more ZEO clients. My circumstance is that the virtual sites are relatively small, they make heavy use of the filesystem blobs and relational database storages to deliberately minimize the size and demand on zodb. I can't see the zodb per virtual site growing to any more than 50MB in size for example. I guess I see the possibility of single ZEO for a number of virtual hosted sites as a plus (since it means also that I could add additional ZEO clients to provide more threads for serving the group of virtual sites). I guess I am just trying to determine the sanity of doing it. I see also with this possible arrangement I could move a zodb out into its own ZEO server and ZEO client situation if it was needed. Many thanks. Regards, David On Tuesday, September 20, 2005, at 02:23 PM, Dieter Maurer wrote:

You can do this -- without ZEO, with a single ZEO (and multiple storages) and with many ZEOs.

Hi Dieter

This was discussed on a zope mailing list (I think "zodb-dev@zope.org"). Please search the archives (via your favorite search engine).

Thanks. I'll look for this.

ZEO is not very RAM hungry.

Only for packing, a higher amount of RAM is necessary.

This is good to know.

Does this not speak for one ZEO server per customer?

Sure does. With a number of sites in a single zeo instance it looks to be essentially the same issue as number of sites in a singe zope instance, you'd have to stop and start as you have pointed out. At the same time it does not seem reasonable to run a separate zope instance and a separate zeo instance for each site where each zodb would not normally exceed 50 MB in my case. So to me it is clear the importance of running separate zodbs per site (but perhaps not as important to have a separate framework whether it be a zope instance or a zeo instance per site). The zodb size has mostly to do with the heavy use of blobs and also relational database storage. But there are still thousands of objects in this situation (and it does not mean any less site maintenance). I am interested in what you might recommend when you are dealing with a number of virtual sites of the smaller zodb scale since this is really the issue I am attempting to solve. I definitely like the features ZEO has to offer as far as asynchronous maintenance, etc. Regards, David

Hi Dieter. I guess the bottom line is to evaluate configurations and weigh them against your resources, needs, risks, etc and then make a decision. The great thing is that Zope is flexible and as a result there are interesting options to consider. Your feedback has been helpful. Many thanks. Regards, David On Friday, September 23, 2005, at 02:03 PM, Dieter Maurer wrote:

David Pratt wrote at 2005-9-22 17:50 -0300:

...

... I am interested in what you might recommend when you are dealing with a number of virtual sites of the smaller zodb scale since this is really the issue I am attempting to solve. I definitely like the features ZEO has to offer as far as asynchronous maintenance, etc.

I have no experience with this.

My experience is with huge ZODB storages -- containing everything, even large binary objects. It copes quite well.

How to proceed with lots of small virtual sites heavily depends on your ressources. If I had plenty of resources, I would each give its own Zope instance -- to make then as independent from one another as possible. If my resource were very tight, I would use a single Zope instance and a single storage to spare resources as much as possible.

-- Dieter