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Date:      Thu, 08 Mar 2001 21:06:11 -0700
From:      Warner Losh <imp@village.org>
To:        cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/release/scripts doFS.sh 
Message-ID:  <200103090406.f2946Bs04692@billy-club.village.org>
In-Reply-To: Your message of "Thu, 08 Mar 2001 17:03:16 PST." <200103090103.f2913GQ88940@freefall.freebsd.org> 
References:  <200103090103.f2913GQ88940@freefall.freebsd.org>  

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In message <200103090103.f2913GQ88940@freefall.freebsd.org> "David E. O'Brien" writes:
:   newfs with `-m 1'
:   
:   This is needed even with `-o space' as the kernel decides to be "helpful"
:   and not really do space optimization.

Space optimization forces the kernel to always use fragments to store
parts of file, rather than using an entire block when less than an
entire block has been written.  This forces files to be as small as
they can be at the minor cost of time to do all the fussy stuff.  The
cpio image that we put on the disk was so close to filling the disk
exactly that this minor minor difference made a big difference.  The
system changed things to time optmization on the first write.  When
the end of file was hit, it tried to allocate a full block (4k), but
there was only 3k left on the disk (since you get only 1407 blocks on
a 1.44 floppy) so it failed.  So this change nails the space
optmiziation in place for the whole operation.  We now have 1k or 2k
free on the alpha disk.

Needless to say, this means that we are right on the hairy edge of
overflowing for the alpha install disk.  I wouldn't be surprised if we
overflow it on the change MFC'd :-)

Talk about an extreme edge case.

Warner

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