Subject Re: [IB-Architect] Shadows questions...
Author Dalton Calford
Our database has signifigantly changed in size.

We started with a single large monolithic design.
Since then we have split the database into historical databases (each
holding 60 days of data) and our current core database which also holds
a 60 day window with records being moved into the historical as needed.
This has increased the overall size of the database due to repetitive
entries across the different historical databases but, each file is now
down to around 12 GB each. (the earlier ones from a few years back only
are about 2 GB each so the growth has been pretty heavy over the course
of the system).

We now have 4 core files and the historical files are kept in both our
ottawa and toronto offices (the users depending on where they logged
into will be told a different historical set).
We keep one core file at the home of my direct boss (he has a dedicated
ISDN hookup into the office) and a core file in Ottawa, Toronto and
The primary core file is in Toronto (the development office) and we
handle and direct conflicts there (we get one about once every couple of
We have automated telephony systems that are clients to the database as
well as having internet and intra-net interbase web access. We have
Delphi and Perl clients connecting in that support our sales force.
Overall, we have alot of disk and network traffic.
Any backup or shadow would be affected by all the activity going on.
So, using any times given by us should be discouraged at all costs.

My suggestion is for you to do some testing on a system that is not live
and see the difference.

I think it is a good tool in the developers tool kit, but, should not be
taken to be the best method around.

I like it because at any time one of our developers asks for a backup to
take place, it takes all of 5 minutes (from the time we tell everybody
we are forking the developement system) to have a complete separite
database that is right up to date with the master.

This is alot better than waiting a few days to get a database that is a
few days out of date.

Hope I have cleared up any confusion.

Best regards


"Leyne, Sean" wrote:
> So your answer is 46 hours in comparison to 52 hours, right? <grin>
> How big is your db? (and can't remember off hand from your previous
> postings...)
> Well, I don't know about you but, that doesn't seem to be much of an
> increase.
> Which makes me questions whether the current "create a backup using the
> shadow process" discussion has any real benefit, within the context of
> enabling a new HIGH-SPEED database backup process.
> Sean
> -----Original Message-----
> From: Dalton Calford [mailto:dcalford@...]
> Sent: Friday, June 23, 2000 1:38 PM
> To:
> Subject: Re: [IB-Architect] Shadows questions...
> Hi Sean,
> That is a very good question.
> You see, when we are using this technique, we have two or three shadows
> going at a time.
> We prune one off which, once the shadow is created, seems to take only a
> minute, and we add another on, but since we already have the backup in
> hand, we do not pay attention to the time it takes to create a new
> shadow.
> When I started playing with shadows (and pestering poor Ann with alot of
> questions about changing page sizes and other such nonsense) I found
> that they seemed faster (by 6 hours or so in comparison to the backup
> process). BUT, please remember, that the only way to take a proper
> reading is to have the shadow file on a separite data bus (scsi channel)
> and to have the whole storage device dedicated to it. Then to try the
> same thing with a backup. And you need to do the comparison without any
> others attached to the database.
> You see, both user and hardware contention can skew the numbers in any
> direction. If you are going to perform tests, you need an environment a
> little less chaotic than what we have here.
> We use this technique for our test databases when we may need to fork a
> database to try a new process or technique while not disturbing the
> developements of others in the office.
> best regards
> Dalton
> "Leyne, Sean" wrote:
> >
> > Dalton,
> >
> > How does the performance of the create shadow compare to performing a
> > full backup of your DB?
> >
> > Sean
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