Re: Cartridge Estimated capacity

The numbers TSM reports are ALL from the server's point of view.

A "filling" tape will have a fixed (and pretty meaningless) EST CAP
determined by the device class until the tape gets marked FULL.  Then TSM
changes EST CAP to the number of bytes actually written to the tape.

With tape drives that can do outboard compression, the TSM server can't
really know how much is going to fit on a tape.  All it knows is how many
bytes it wrote on the bus to the tape drive before the drive signalled back
that the tape is full.

So if the clients aren't compressing data, and TSM is writing to a tape
drive that is doing compression, you can get HUGE variations in the amount
of bytes TSM reports sending to a tape.

Some data compresses better than others.  For example, ASCII text files
compress a whole lot, but .gif and .tif and .zip files are already
compressed, so they usually don't compress more when sent out to the drive.

If the client compresses the data FIRST, you see less variation in the
amount of bytes written to your tapes, because they data doesn't compress
much more when sent to the drive.

Your stats look normal to me.

-----Original Message-----
From: Robert Ouzen [mailto:rouzen AT UNIV.HAIFA.AC DOT IL]
Sent: Thursday, January 22, 2004 11:46 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Cartridge Estimated capacity


Hi to all

Can anybody tell me why the huge difference between  the numbers of
Estimated Capacity  of a full cartidge DLT8000 (40/80 G). The format of the
devclass was configure to DRIVE.
The nodes are backup without compression .

Here the output of the q vol.

Volume Name               Storage      Device      Estimated    Pct   Volume
                          Pool Name    Class Name   Capacity   Util   Status
                                                        (MB)
------------------------  -----------  ----------  ---------  -----
--------
000002                    SCA_UNIX     SCALARCLA-   58,089.8   96.5    Full
                                        SS
000009                    SCA_UNIX     SCALARCLA-  165,222.0   64.6    Full
                                        SS
000016                    SCA_UNIX     SCALARCLA-   76,230.3   49.1    Full
                                        SS
000027                    SCA_UNIX     SCALARCLA-   65,272.7   40.9    Full
                                        SS
000034                    SCA_UNIX     SCALARCLA-   80,000.0    3.9  Filling
                                        SS
000044                    SCA_UNIX     SCALARCLA-  136,684.2   62.8    Full
                                        SS
000111                    SCA_UNIX     SCALARCLA-   48,768.3   44.5    Full
                                        SS
000141                    SCA_UNIX     SCALARCLA-   51,704.7   40.6    Full
                                        SS
000158                    SCA_UNIX     SCALARCLA-   70,574.6   97.3    Full
                                        SS
000159                    SCA_UNIX     SCALARCLA-   80,000.0   62.9  Filling

T.I.A Regards
Robert Ouzen
E-mail: rouzen AT univ.haifa.ac DOT il