[Zope] Zope Myths?

[sean.upton@uniontrib.com]

I strongly considered this option at one time with a shared DAS/RAID between
my primary and secondary ZSS.  I never ended up doing this because of
concerns.

Out of curiosity, with shared storage over SCSI/SAN, do you have any
thoughts on how to overcome the following issues?

1 - Data fencing (using SAN switches+integrated software, or STONITH
devices, or something)??
2 - Clean up a broken FileStorage?  To what degree can this be successfully
automated without manual intervention of a sysadmin?
3 - Deal with accidental damage to the storage done by the primary node,
perhaps due to asynchronous writes to the file?

It really seems like replication is really a less brittle option (though how
much less brittle, I'm not sure).

Though not committed at this point, for a big project I am working on, I am
strongly considering use of DirectoryStorage and its snapshot capabilities
for low-tech replication (via find+cpio+nfs) to try and minimize issues I
might face similar to #2 and #3 if I had chosen FileStorage.

Sean

-----Original Message-----
From: Bill Anderson [mailto:bill@libc.org]
Sent: Wednesday, September 11, 2002 3:20 PM
To: Paul Winkler
Cc: zope@zope.org
Subject: Re: [Zope] Zope Myths?


On Wed, 2002-09-11 at 09:54, Paul Winkler wrote:
> On Wed, Sep 11, 2002 at 03:01:14PM +0100, Paul Browning wrote:
> > What have we understated/exaggerated/misunderstood?
> 
> AFAIK, ZEO still does not allow you to distribute your ZODB.
> There is still a single, central ZEO server with a single
> ZODB.

Actually, using shared storage, such as one may have on a SAN, or using
a shared SCSI bus (I *strongly* recommend the FC-SAN route over the
shared SCSI ;), and a fail over server setup, you can indeed provide
fail-over ZODB services.

Yes, I know fibre channel SANs are beyond the means of most on the list,
but it is certainly possible.

In fact, I know of a way to provide multi-site fail over using ZODB and
SAN technology on Linux. In fact, if one had one of the IBM zSeries
boxes ... mmm toys ....

I've yet to try it out (looking for a new job takes too much time in
this market), but I believe one could use this method and provide
multiple read-only ZEO servers for the same DB.

-- 
Bill Anderson
Linux in Boise Club                  http://www.libc.org
Amateurs built the Ark, professionals built the Titanic.
Amateurs build Linux, professionals build Windows(tm).


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