[Zope-dev] HA storage for zope

[Miles Waller]

Hi,

I'm looking at a HA setup for a project, and was wondering what the current
best way forward would be.  There seem to be a few potential options around
for the storage end of the setup, and I'm wondering what's now considered
the current "best practice" for this sort of setup.  Specifically, I've come
up with three options:

1. RelStorage
Using this, I think I can then take care of replication/mirroring as I have
access to a database that is already clustered in a HA environment.  My
questions are:
 + Are the connections opened only when zope is started?  Say I unplugged a
network cable and then plugged it back in again (breaking the database
connection) - will it be re-opened?
 + How does RelStorage take care of the blob storage?
 + Are there any details of big sites out there that use RelStorage
(particularly on Oracle)?

2. ZeoRAID
I could use ZeoRAID to write to maintain several independent storages
subject to stopping the ZeoRAID server being the single point of failure (I
posted some questions about this separately).

3. ZRS
If I'm right, ZRS still has a limitation in that there is a single server
for writes.  Also, budget may be an issue.  Having read the factsheet, I'm a
bit unsure as to how it is functionally different from ZeoRAID - can anyone
explain?

I also thought of using DirectoryStorage to take care of
replication/mirroring at the hardware level, for example using a clustered
SAN, but I think this would not work because the actual directory tree can
only be writeable by one zope at a time.  Am I right about this?

Is there anything else worth considering?

I'd be grateful if anyone operating a HA-setup for their zope site, could
post your setup and experiences?  To me, out of the above options,
RelStorage looks to be the most promising, simply because it will involve
the least setup and the database clustering and tools are pretty robust and
well-understood by the sql experts here.

Thanks in advance for your help, I will post a write-up once it's done,

Miles