Advice for hacking on ufs/ffs
olli at lurza.secnetix.de
Fri Jul 28 09:27:55 UTC 2006
Rick C. Petty wrote:
> Dag-Erling Smørgrav wrote:
> > Rick C. Petty wrote:
> > > Shane Adams wrote:
> > > > I used dd to create 1G file.
> > > A faster way is:
> > > touch filename
> > > truncate -s 1g filename
> > no, this will result in a fragmented image, which will hurt run-time
> > performance.
> Not necessarily. If you install a variant of windoze, the installer will
> format the disk first, writing zeros (and metadata) sequentially, and
> thus the allocation will not be fragmented.
Not true. Last time I installed Windows, it did not
overwrite the whole disk. If it did that, it would
have taken _way_ too long (hours instead of minutes).
> In the case of UFS newfs
> only the metadata will be written for each cylinder group
No. Only the superblock copies and block bitmaps are
written during newfs, nothing else.
> and thus the
> logical blocks for all metadata will be contiguous.
Nope. As soon as you start writing to such a file system,
it will start allocating space for inodes, indirect block
lists, directories and file data, which will probably lead
to massive fragmentation.
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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