[ZODB-Dev] Handling more databases with zeo

[Tim Peters]

[Tim Peters]
>> As before, I'd run a different ZEO server for each database.  I'm not
>> sure that what you're doing here will be supported for much longer (or
>> really even _is_ supported anymore -- see my last msg).

[Lukas Linhart]
> Well, I'm stuck on zodb 3.2.x line because I'm using IndexedCatalog.

If serving multiple databases from one ZEO server works for you, I'm not
going to go out of my way to break it (OTOH, if it doesn't work for you, I'm
not going out of my way to fix it either).

...

> I think I'll run zeo per db, just for sure :) I don't think it that my
> serveradmin will be happy, but...whatever :)

Well, another ZEO is another process -- doesn't sound like a big deal to me.
In "industrial strength" setups, it's normal to run multiple ZEO servers on
multiple machines, or at least to arrange that each database lives on a
different physical disk drive.  A ZEO server doesn't cache any object state
in memory, so if it's using FileStorage it needs to seek in the .fs file on
each object request.  That can get pretty dreadful if it needs to do
physical seeks in multiple database files on the same disk simultaneously.
Putting each database on a different disk makes life easier for the HW
(seeks can proceed truly in parallel then); putting each on a different
machine gives OS disk caching a better chance at avoiding physical disk
seeks.