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Date: Thu, 10 Nov 2016 16:38:39 -0800 (PST)
From: "Peter A. Castro" <doctor AT fruitbat DOT org>
To: Erik Soderquist <ErikSoderquist AT gmail DOT com>
cc: cygwin AT cygwin DOT com
Subject: Re: Complaining after fair notice of dropping XP support. Was: Not very nice at all.
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On Thu, 10 Nov 2016, Erik Soderquist wrote:

> Date: Thu, 10 Nov 2016 17:16:53 -0500
> From: Erik Soderquist <ErikSoderquist AT gmail DOT com>
> To: cygwin AT cygwin DOT com
> Subject: Re: Complaining after fair notice of dropping XP support. Was: Not
>     very nice at all.

Greetings, Erik,

> On Thu, Nov 10, 2016 at 2:19 PM, Peter A. Castro wrote:
>> And for those who think keeping a private mirror is trivial, let me give you
>> some stats.  A full snapshot of Cygwin, 32-bit + 64-bit (+noarch) + source
>> packages (Current and Previous) is about 137Gb.  Don't believe me? Your
>> setup.ini has a size (and a hash) for every package.  Add them up yourself.
>> Now consider that I have about 4000 snapshots (and counting!) of Cygwin.
>> Oh!  Quick quiz:
>>   What's 137Gb * 4000?
>>   Answer: 535Tb.
>> Now, do you really think I have that amount of storage?  Of course not. The
>> Time Machine isn't organized like that (don't be silly).  It's currently
>> about 500Gb (which is quite a savings, if you think about it :-)
>
> I would dearly love to know more about how you did this specific piece...

A good magician never reveals how the trick works.  8^)

Sadly I'm not a good magician.

It's not all that complicated, if you think about it.  Each time a new 
setup.ini is generated only a hand full of packages was actually updated, 
so really, day-to-day, there's not all that much change.

I keep a delta database and each time I grab a new setup.ini I compare all 
of the packages listed to my existing database.  Anything new, I pull down 
and add to the archive.  Anything already present I don't re-pull.  Think 
of it as de-duplication on a package level (though I do this for more 
than just setup.ini, but that's a separate trick).

It's only if you decide you want a complete copy of all packages for any
given circa that the amount of data instantiating is alot.

Then, from the setup.ini, I create a new circa directory and, really, the 
smoke-and-mirrors of the trick is that it's all symlinks to the real 
package storage, of which I have exactly one copy.  Hence, 500Gb 
instead of 535Tb.

So, um, "Ta-da"! :-)

Oh, this is all automated, btw.  I hardly touch it except to clean out 
old logs and do backups from time to time.

Sorry, it wasn't all that good a trick, was it.

> -- Erik

-- 
--=> Peter A. Castro
Email: doctor at fruitbat dot org / Peter dot Castro at oracle dot com
 	"Cats are just autistic Dogs" -- Dr. Tony Attwood

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