----- Original Message ----- From: "Martijn Pieters" <[EMAIL PROTECTED]>
To: "Jonathan" <[EMAIL PROTECTED]>
Cc: "Brian Brinegar" <[EMAIL PROTECTED]>; <zope@zope.org>
Sent: Thursday, September 14, 2006 2:54 AM
Subject: Re: [Zope] ZEO with Multiple Storages

On 9/14/06, Jonathan <[EMAIL PROTECTED]> wrote:
If you mean having zope commit a single transaction to multiple storages,
then 'vanilla' zope won't do it (Zope Corp has a commercial product called
ZRS which does this type of thing).

No, that's not true. ZRS is used to create hot read-only or stand-by
copies of a ZEO server (and all storages within such a server are

One ZEO server can deal with multiple storages just fine. Transactions
involving multiple storages commit just fine.

Yes and No!

Yes: a single zeo server can deal with multiple storages (ie. a storage can contain mount points to other storages)

Yes: if a single transaction creates/modifies multiple objects and each of those objects is stored in a different storage (all storages 'served up' by a single zeo server), then the single transaction will commit those objects to their respective storages with no problem. (however, there are little/no performance improvements in this scenario)

No: if a single transaction creates/modifies a single object, that single object can not be stored over multiple storages (ie. you cannot achieve RAID 'disk striping' type of performance improvements)

However, that being said there may be some improvement, if the application is disk-bound, by giving each storage its own disk subsystem (never tried this myself, but it may buy some small performance improvement). For the cost/effort involved I would stick to having a single zeo server 'serve up' a single storage, and have each zeo server on its own hardware platform (much more scalable, easy to implement).


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