ADSM-L

Re: I don't think she can hold much more Captain! She's gonna blow! (IBM LTO Tape)

2001-08-28 19:07:12
Subject: Re: I don't think she can hold much more Captain! She's gonna blow! (IBM LTO Tape)
From: Joerg Pohlmann/CanWest/IBM <jpohlman AT CA.IBM DOT COM>
Date: Tue, 28 Aug 2001 16:01:45 -0700
I have seen exactly the same type of results. One of my customers routinely
gets 250+GB per tape; and in one other instance my customer got 400+GB,
similar to what you are experiencing. Compression results are a function of
the type of data. If you are using collocation, the compressability becomes
more obvious for the type of data because a given node is clustered on a
cartridge. For example if your clients compress their data, you will find
tape capacities much closer to 100GB. In my case, the 400+ GB client was an
API database client that sent very compressable data.

Remember that the total amount of data written to the tape only shows up
when the tape is marked "full". When it is "filling", TSM will keep on
writing to the tape and you will see the Estimated Capacity increase.

Joerg Pohlmann



Jim Taylor <jtaylor AT ENLOGIX DOT COM>@VM.MARIST.EDU> on 2001-08-28 15:47:29

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

Sent by:  "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>


To:   ADSM-L AT VM.MARIST DOT EDU
cc:
Subject:  I don't think she can hold much more Captain! She's gonna blow!
      (IBM LTO Tape)


How much can these 100GB native tapes hold?

Can I really be getting this kind of compression?

Half a TB on one tape?  Anyone else seeing this?

My real issue is with the Status.  It says that the tape is still filling,
yet its Pct Util is only at 95%.

I don't get this.  I thought that a tape get to 100% full and the Est Cap
keeps increasing until EOT is met.  At which time the Status changes to
Full
and the Pct Util can then drop from 100% as the data on the tape expires.

Have I been wrong???



tsm: TSM-D2>q vol

Volume Name               Storage      Device      Estimated    Pct
Volume
                          Pool Name    Class Name   Capacity   Util
Status
                                                        (MB)
------------------------  -----------  ----------  ---------  -----
--------
--------
/tsm/tsmstg/disk-vol01    DISKPOOL     DISK          5,000.0   30.5
/tsm/tsmstg/disk-vol01    DISKPOOL     DISK          5,000.0   30.5
On-Line
A00000                    TAPEPOOL     LTOTAPE     100,000.0    7.2
Filling
A00007                    TAPEPOOL     LTOTAPE     204,800.0    2.6
Filling
A00023                    TAPEPOOL     LTOTAPE     384,482.9   65.0    Full
A00031                    TAPEPOOL     LTOTAPE     398,471.2   64.4    Full
A00035                    TAPEPOOL     LTOTAPE     537,664.2   85.3
Filling

tsm: TSM-D2>

> Jim Taylor
> Senior Associate, Technical Services
> Enlogix
> *  E-mail: jtaylor AT enlogix DOT com
> *  Office: (416) 496-5264 ext. 286
> * Cell:  (416)458-6802
> *   Fax: (416) 496-5245
>
>
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