Re: need for in-place upgrades (was Re: State of Beta 2)

Marc G. Fournier wrote:
> 'k, but is it out of the question to pick up a duplicate server, and use
> something like eRServer to replicate the databases between the two
> systems, with the new system having the upgraded database version running
> on it, and then cutting over once its all in sync?

Can eRserver replicate a 7.3.x to a 7.2.x?  Or 7.4.x to 7.3.x?

Having the duplicate server is going to be a biggie; in my own case,
where I am contemplating a very large dataset (>100TB potentially), I am
being very thoughtful as to the storage mechanism, OS, etc.  eRserver
figures in to my plan, incidentally.  I am still in the early design
phase of this system; PostgreSQL may just be storing the index and the
metadata, and not the actual image data.  In which case we're only
talking a few million records.  The image data will be huge.  While I
_will_ have a redundant server (in a separate building), I'm not 100%
sure I'm going to do it at the application level.  As I have vast
amounts and numbers of 50/125 mm fiber run between buildings, as well as
a good amount of singlemode, I may be running a large SAN with Fibre
Channel (depending upon how cheaply the switches and HBA's can be
acquired).  I already have in place a fully meshed OC-12 network, which
I am expanding, to meet the regular data needs.  But ATM on OC-12 is
suboptimal for SAN use; really need fibre channel.

Now before anyone gets the idea that 'hey, you got money; buy another
server!' you might want to know that PARI is a non-profit; those OC-12
switches are either donated or surplus 3Com CoreBuilder 7000's
(available ridiculously cheaply on eBay), and the fiber was already here
when we acquired the site.  We are not rolling in dough, so to speak.
So there will be no surplus drives in the array, or surplus CPU's
either, to run a spare 'migration' server.  And I really don't want to
think about dump/restore of 100TB (if PostgreSQL actually stores the
image files, which it might).

As most everyone here knows, I am a big proponent of in-place upgrades,
and have been so for a very long time.  Read the archives; I've said my
piece, and am not going to rehash at this time.
--
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute