[hfs-user] To Calculate the size of Catalog File for creating a Readonly Filesystem

Biswaroop(External) Biswaroop\(External\)" <biswaroopb@integramicro.com
Mon, 13 May 2002 17:29:06 +0530


Hi everybody,

 I  want some help in finding a approximate value of the extents file.
 Let me describe it...
 I  HAVE the following information

-->>   Total no. of directories present in the volume

-->>  Total no. of files with their full path and size in bytes.

-->> The total amount of  space needed for the data of those files.


Problem faced ::  Till  now I used  to find the total volume size first
since i knew the size of each file. And then as in the Linux implementation
                           they keep 1/128 th part of  the Volume size as
the size of the Catalog File. The problem was when I used to select
                           some directories for eg. DDK folder whose total
size is around 58 MB and has around 4300 files in 300 directories.
                           The Catalog file size decided upon the volume
size would fill before all the entries were made and hence I would be
                           left wtih an incomplete filesystem.
                           I  manipulated with different fiqures for the
Catalog file size but it was more a hit and trial method.
                           I know that Catalog File has information of the
whole directory structure of the volume in a B* tree format.
                           I also know at any given timeshot the B* tree
will be around 2/3 rds full.

                           I now know the size of the Catalog File depends
actually on the no. of  File and Directory entries rather than the full
Volume size.
                           So, can anybody give me a simple formula ( may be
a good approximation)  in trying to find out the Catalog File size needed
                           for a given volume when I have the information as
mentioned above.
                           Such that  the file size may be bigger than
actually needed but not exceedingly big. In other words is there any way to
find out
                           the size from no. of Directory entries and file
entriee???

                          Waitng for help .

                          Bye
                          Biswaroop




















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