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Message Posted: Fri, 05 Mar 2004 @ 07:54:10 GMT


     
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Subj:   Re: Do we lose available DiskSpace if we change the number of AMPs?
 
From:   Dennis Calkins

Hi,

The calculation for DBC SPACE is based upon the SMALLEST AMP * number of AMPS.

if you have 10 36 GIG amps you will have 360 GIG (10 * 36 ) of DBC space at trhe start of the world ( minus some over head ).

If you then take and add 10 30 GIG amps you will have 600 GIG of DBC space

20 * 30 (smallest amp size))


Therefore you didn't really lose any space, you just didn't get the full

10 * 36 ( 360 ) + 10 * 30 (300) == 660 Gig of space you were expecting.


The reason this is done this way is given a PERFECT system, every table will be perfectly distributed across every AMP equally. Therefore when the SMALLEST AMP reaches capactity it can't accept any more rows.

Why should those HASH codes be told they can't be added, when other HASH codes which reside on the other AMPS ( with 36 gig amps) be allowed to continue to be inserted. That would skew the data.

Therefore when the smallest AMP fills up the whole system is considered full.



     
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