Does geom_uzip act as a variable size storage device?
Pawel Jakub Dawidek
pjd at FreeBSD.org
Thu Feb 10 04:44:45 PST 2005
On Wed, Feb 09, 2005 at 06:39:19PM -0800, Loren M. Lang wrote:
+> How does the uzip geom work as a block device for a file system. My
+> understanding of it is that it operates like a block device that trys to
+> compress all data written to it using the same algorithm as used by
+> pkzip and gzip. The problem I see with that is that not all data
+> compresses by the same amount, some compresses more and other less, so a
+> disk that acts as a compressor can hold different amounts of data
+> depending on what's written to it. Filesystems like msdos and ufs2
+> don't support running on block devices of variable sizes as far as I know
+> so how can I possibly format a uzip disk with a regular filesystem. I
+> know that ufs supports being resized, but that's not the same as a block
+> device that appears to be constantly changing size as data is being
+> written to it so how does uzip work? Does it appear as some fixed size
+> that may have wasted space if the data was able to compress really well,
+> and when the data doesn't compress well enough, well, I don't know what
+> would happen then.
+> Am I just missing something here or can the uzip geom be dangerous
+> depending on how it's used and what fs it's formatted as.
You cannot write to geom_uzip's providers.
So you need to create provider image (compress your file system) and
geom_uzip exports it as read-only provider.
Pawel Jakub Dawidek http://www.wheel.pl
pjd at FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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