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Old 03-28-2006, 08:56 AM   #1
pixellany
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extended partitions


In a recent discussion, I suggested that one can have more than one extended partition in the first (and subsequent) partition table. Some responders concurred.

I then tried to do it, and none of the tools on my machine will do it. They allow only one extended partition in the first table. Then--MANY logical partitions are allowed. (Each one goes in a separate partition table---ie the first table is the only one with 4 entries allowed)

Interesting nuance: It seems that--every time a logical partition is added, the tool also creates another extended partition in the same table. Is this then the link to the next logical partition?

What sets the limit on the total # of partitions in one drive?
 
Old 03-28-2006, 09:20 AM   #2
demian
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There can only be four primary partitions one (and only one) of which maybe an extended partition (an extended partition is nothing but a primary partition that can be subdivided into logical partitions).
Logical partitions are implemented as linked list so every logical partition contains a pointer to the next. In principle there's no limit on the number of logical partitions. However, in linux there is. Last time I checked you could have 15 usable partitions on a scsi disk (3 primary, 12 logical + 1 extended (which cannot contain a filesystem)) and 63 on an ide drive (3 primary, 60 logical + 1 extended). I'm not exactly sure where this limit comes from but my guess is that it's a size limit of the array that holds the pointers to the partitions.
 
Old 03-28-2006, 09:24 AM   #3
pixellany
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Quote:
Originally Posted by demian
Logical partitions are implemented as linked list so every logical partition contains a pointer to the next. In principle there's no limit on the number of logical partitions. However, in linux there is.
What you are saying is that one could create more partitions, but then Linux would not see them??
 
Old 03-28-2006, 09:36 AM   #4
demian
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Actually I don't know what happens if you surpass that limit with a partitioning software that allows it and then try to access them in linux. I don't have a scsi disk to test that with and don't really feel like creating 65 partitions on an ide disk to find out. You tell me
 
Old 03-28-2006, 03:05 PM   #5
pixellany
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Quote:
Originally Posted by demian
Actually I don't know what happens if you surpass that limit with a partitioning software that allows it and then try to access them in linux. I don't have a scsi disk to test that with and don't really feel like creating 65 partitions on an ide disk to find out. You tell me
At this point it is curiousity for which I will exert very limited energy. When I decide to follow one of our gurus (Saikee) and set up a system with over 100 OSes---then maybe.....
 
  


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