I would say you are forgetting the i-nodes. Unix filesystems dynamically
allocate i-nodes describing the physical file layout. In AIX (and not
only) the default settings are optimized for small files. Therefore a
large file like dbvol consumes a lot of i-nodes, i.e. 512b blocks.
You can attempt filesystem creation with larger "-a nbpi" value or attempt
to use 2933MB. In latter case if you substract from 3008300 the sum of
dbvol size and free blocks you can find how many blocks have been used for
i-nodes.

Zlatko Krastev
IT Consultant






Roger Deschner <rogerd AT UIC DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
20.02.2003 20:18
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        DSMFMT space calculation mystery


I've got a problem of not having the right mathematical formula. My
problem is that, when planning a new TSM data space for Log, Database,
or disk storage pool volume, I cannot figure out the maximum
size I can allocate. I'm using AIX 4.3.3.ML9 with TSM 4.2.2.8.

Step 1) Use the OS to create a Unix file system of the appropriate size
and characteristics. The Unix "df -k" command (allegedly) tells me how
big it is and how much space is in it:

Filesystem    1024-blocks      Free %Used    Iused %Iused Mounted on
/dev/kumquat      8781824   3008300   66%       18     1%
/usr/local/kumquat

Step 2) Format it. The following calculations are from "TSM
Administrator's Reference". 3008300k/1024=2937m Rounding down to a
multiple of 4mb gives you 2936m. Adding 1 for overhead gives you 2937m.
However, specifying

dsmfmt -m -db /usr/local/kumquat/db12 2937

It formats for a long time and then abends with message:

Error writing file /usr/local/kumquat/db12, errno = 28

...which means, not enough space.

Where are my calculations going wrong? I can try to reduce the number a
few mb at a time and figure this out by trial and error, but this takes
literally DAYS of my time. So I usually guess at 98% and waste some
space. How can I really calculate this?

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu
============ "The World's Least Intuitive Operating System" ============
=============== -- from the cover of "Unix for Dummies" ================