Text 21787, 33 rader
Skriven 2006-10-02 18:26:08 av Jeff Guerdat (1:275/311)
     Kommentar till en text av Dan Ceppa
Ärende: Re: Outlook Express & network
=====================================
Dan Ceppa wrote:
> -> On 01 Oct 06  13:09:08, Jeff Guerdat got back to Björn Forsström 
> -> Re: Outlook Express & network
> 
>  JG> Most email clients "compress" the various folders but it's not the
>  JG> type  of compression you're thinking about.  As the messages are read
>  JG> and  deleted, dead space occurs within the file (I never found out
>  JG> why).  
> 
> It's not really a dead space in the file.  It's available free space 
> that is still allocated, thus unusable at that point.  It all has to 
> do with the FAT.  A 1 bit file takes up the same space as a 1K file.  
> (at least in this illustration.  FATS do vary by OS.)  Thus, depending 
> on how things were first written and then deleted, it is possible that 
> 1,000 1 bit records can consume 1MB of disk space.  Rewritting those 
> records into a single file can, conceivably, make it into a 
> single 1K file.  

Most (all?) email clients keep the mail in a single file with new 
messages appended to the end of the file.  When you delete a message, it 
gets pulled out of the middle of the full file and the file is rewritten 
to reflect that.  Obviously, a size is allocated in the file system for 
the original file and must be recalculated for the modified one. 
However, the action you see take place is a function of the application, 
not the file system (Firefox, f'rinstance, displays a bar to show the 
progress which is easily monitored if you have a large message file, 
with the disk busy the whole time, not something the file system would 
need to do).

Does every client do the same thing the same way?  I have no idea but 
they seem to be similar...
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