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Date:      Mon, 2 Apr 2001 15:04:39 -0500
From:      Andrew Hesford <ajh3@chmod.ath.cx>
To:        Dru <genisis@istar.ca>
Cc:        Andrew Hesford <ajh3@chmod.ath.cx>, FreeBSD-questions <freebsd-questions@FreeBSD.ORG>
Subject:   Re: disklabel and block size
Message-ID:  <20010402150439.A2803@cec.wustl.edu>
In-Reply-To: <Pine.BSF.4.21.0104020744030.14163-100000@istar.ca>; from genisis@istar.ca on Mon, Apr 02, 2001 at 07:47:12AM -0400
References:  <20010402023151.A817@cec.wustl.edu> <Pine.BSF.4.21.0104020744030.14163-100000@istar.ca>

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On Mon, Apr 02, 2001 at 07:47:12AM -0400, Dru wrote:
> 
> Hi Andrew,
> 
> You might find the following article helpful:
> 
> http://www.oreillynet.com/pub/a/bsd/2001/02/28/FreeBSD_Basics.html
> 
> This was the 2nd article in a 3-part series, so you might want to scan the
> other 2 as well.
> 
> Cheers,
> 
> Dru
> 
> 
> On Mon, 2 Apr 2001, Andrew Hesford wrote:
> 
> > I have two related questions:
> > 
> > 1. In the disklabel output, what is the significance of the bps/cpg
> > group? The man page for disklabel says that for disks larger than 1G, it
> > defaults to 64, but mine is 16, and an example in the man page had it
> > set at 75. What does this field mean, and how will different values
> > affect the disk?
> > 
> > 2. All my filesystems have block sizes of 8k and fragment sizes of 1k.
> > What does this mean? For ext2 and fat, a block is the smallest
> > allocatable disk segment, meaning that I can store at most 1 file in
> > each 8k block. However, the fragment suggests that the smallest
> > allocatable segment is 1k, with block having a different meaning. Can I
> > store up to 8 files in each 8k data segment, or only 1 file?
> > Furthermore, if the fragment is the smallest allocatable group (in the
> > sense of an ext2 block), what is the significance of an FFS block? Is it
> > the amount of space that is reserved for file writing in order to prevent
> > fragmentation of data?

Thanks a lot, it answered part two of my question perfectly. I'm still
wondering about the cpg field in the disklabel. I notice in your
examples the field simply contains a "#", whereas mine are 16.

I've looked through some of your articles on oreillynet, I really enjoy
them. Keep up the good work!
--
Andrew Hesford
ajh3@chmod.ath.cx

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