[Zope] Zope Myths?

[Bill Anderson]

On Thu, 2002-09-12 at 00:21, tomas@fabula.de wrote:
> On Wed, Sep 11, 2002 at 03:46:43PM -0700, sean.upton@uniontrib.com wrote:
> > 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.
> > 
> [...]
> 
> > It really seems like replication is really a less brittle option (though how
> > much less brittle, I'm not sure).
> > 
> 
> Hear, hear... Besides, you still have a single point of failure: your SAN
> system. OK, it's expensive and may thus fail less, but then you might buy
> an expensive system to begin with ;-)

Well, in that case, your network is a single point of failure, too. :^)
Expensive, well that depend son what you are doing. For under 35000 you
can have just shy of a 1TB of file space, with snapshot capability,
multi-machine fail over, and a whole lot more. That cost includes two
machines running Linux with fail over. It depends on your needs, and
your uptime/availability requirements.

For example, if you are running a site like cbsnewyork.com, 25-35 grand
is not that much. If you are running a small site, then you don't need
it. My point was that it (it being ZEO/ZODB/ZOPE) _can_ scale to that.
I've done it.

> 
> Another experience I had with such semi-high-end thingies is: if you haven't
> (some access to) experience with this very configuration, unexpected problems
> tend to crop up, thus eating up the advantage you thought to have. You are

Well, speaking as a former tester of SAN technology, it would appear
things have changed dramatically since your experiences. :)

The configuration/setup is essentially the same as with SCSI, in fact,
Fiber channel uses the SCSI subsystem in the OS. The underlying system
is as robust as the SCSI system, since it is SCSI just over a different
medium.


> dealing with a more exotic system, with a smaller installed base, remember.
> You better know you understand very well how it works (or you have access to
> someone who does). Don't believe what marketing says -- those guys are in
> bed when one of your SCSI disks in the array fails and the RAID controller
> thinks it hasn't a hot spare and it'd better shut down the system (I had this
> one too -- luckyly I don't sell myself as hardware guy ;-)

I've never seen this with the Fiber Channel Arrays I dealt with. But
then again, they had two or more controllers. :^)


> 
> > 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.
> 
> I'd tend myself too to low-tech replication solutions -- in spite of the
> issues they present. Besides, if the systems are far apart, they still
> work if one of the buildings catches fire =:-0

Same thing with fibre channel SAN tech, the range is measured in miles.
I know of several SANs that are spread over multiple states. You can
literally have a fail over datacenter.


-- 
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).