Problem statement :  A Generic API ...thus resulting into lean binary base of the software-module (for backup, volume-management) 

                     derstanding data-Backup solutions,

                     volume-management solutions where ...data resides on disk based medium.

                     a understanding of implementations of virtual-memory or paging as a concept.

                     a understanding of fileystem ...generation of a address-map...for the disk-medium

                     a understanding of how the 'dd' command works.

                     Read through projects.pdf, also else-where as envisaged by this author,
                     various contexts that may be relevant to the subject.

                    
Opportunity :  In most cases given that data is stored on disk based mediums, given that all I/O to such

               medium is buffered ...i.e. IO blocking ....in the most instances,

               ...data on the disk can bifurcated to 'pages' of data , on any active data-store's ...data is subject

               to modification i.e. data on medium is constantly modified 

               ....by using the concept of 'dirty-page-logging' (refer to any standard database design and implementation to

               understand the concept),


               understanding various kinds of backup's in vogue viz. incremental, differential, full.


               Requirement's for implementing a solution or api that caters to

 
               'IO' level daemon ...that implements and takes care 'dirty-page-logging' i.e. journal every page modified or appended,
                or start-end ranges byte blocks either modified or appended.

                a log of all dirty-pages....given the context require's...flagging of each 'dirty-page' in the log with
                purpose( the perl anonymous ...hash's provide's decent mean's of implementing or logging , tracing the
                activity...viz. piping or synchronizing data i.e. 'dirty-pages' to mediums.).


                A full-back-up  or 'a snapshot' or a disk synchronized with a active volume ,
                ....offer's the base or starting point for implementing dirty-page logging.



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Note: The above problem statement having been encountered in various scenarios
      and detailed in various 'Proof of concepts' as mentioned in 
      
       http://uk.geocities.com/ravivenkatus/projects.pdf
       http://ravishankarkv.tripod.com/projects.pdf
        ....apply appropriate
      'use-case' modeling, rationalize and arrive at a workable and feasible 
       solution both commercially and techinically viable.