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Re: Best partition distibution for new install.

On Wed, 19 Nov 1997, robert havoc pennington wrote:

> On Wed, 19 Nov 1997,  Raymond A. Ingles wrote:
> >
> >  The second thing to think about is the PC's somewhat dated partition 
> > scheme. You can only have 4 physical partitions on a drive, but you can 
> > divide those partition into logical partitions. All things being equal, 
> > it's better to avoid logical partitions if you can. It's also simpler for 
> > you, the installer. :->
> > 
> How hard should I try to avoid logical partitions? What's the impact
> of using them?

 Well, logical partitions reside inside physical partitions, obviously. 
(Forgive me if I go over some basics; other people may be reading this.)
The drive has a physical partition table at the start of the disk, which 
specifies where the partitions are, and has space for four entries.

 Then, inside a physical partition, you can put another partition table 
and make logical partitions. You further subdivide the physical partition 
into logical chunks.

 This does defeat one of the purposes of splitting things into 
partitions, though. If you put all your eggs in one basket by using one 
giant partition, and something screws up that partition, you are hosed - 
everything's lost. Splitting things up into separate partitions limits 
your risk - most likely only one partition at a time will go, and 
recovery is easier. With logical partitions, though, you don't have quite 
the same protection. A single error on the physical partition can hose
all the logical partitions in it.

 Then there's the performance question, which, I'm sorry to say, I'm not 
too clear on. I always thought that the logical partitions were at least 
physically separate within the partition, like so:

 [-----------------][-------------][(logical 1)(logical 2)][-------------]
  phys. part. 1      phys. part. 2  phys. part. 3           phys. part. 4

 But I've also heard that logical partitions can interleave with each 
other, like fragmented disk files. If that's really the case, then the 
performance hit could be fairly substantial, and the risk of data loss in 
case of an error even greater.

 I'm curious now, and I'm going to investigate it. I'll let you know what 
I find. If someone reading this knows the answer, please let us know.

> I'm about to get a new mainboard and disk to replace my trusty 386sx,
> and I was hoping to use more than four partitions.

 Well, I've used them before (*way* back when Linux only supported 16MB 
swap partitions). I made a 32MB physical partition and split it into to 
16MB logical partitions. I never noticed any problems from that. 

> Another question: I was thinking of installing both stable and unstable.
> They can be rescue partitions for one another, and if unstable does 
> weird things while I need to get some work done I can abandon ship and
> switch to stable. Also I can play with unstable without fear of destroying
> my only system. :)

 Another benefit from using partitions. :->

> Anyway, I'm hoping to share /home, swap, and /tmp between the two systems.
> Are there any other directories I can share? Maybe /usr/local? Is this a 
> good idea in general? Anything I should consider before trying it?

 If you're going to be installing different versions of packages, you 
should probably not share any more than the first three. Sharing /usr and 
/usr/local would mean you'd have a mix of stable and unstable packages, 
and unless you're careful about it, that could lead to lots of 


 Ray Ingles          (248) 377-7735       ray.ingles@fanucrobotics.com

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