Veritas-bu

[Veritas-bu] NetBackup tape usage

2000-08-11 09:22:44
Subject: [Veritas-bu] NetBackup tape usage
From: John Brooks jobrooks AT winstar DOT com
Date: Fri, 11 Aug 2000 09:22:44 -0400
Charles,
  The amount of data that fits on the tape depends on the data's
compressibility.  Hardware and software compression algorithms work
generally by eliminating redundant data and making the storage more
efficient.  Different types of data have widely different levels of
compressibility.  Text files and any file with lots of 'empty' space
(long runs of repeating characters, such as nulls or spaces) will
compress very well.  Binary data that looks almost random to the eye
won't compress much (if at all).  Program executables are usually
somewhere in between.  Files that have been previously compressed with
gzip or winzip usually won't compress at all, and may even expand
depending on how smart your compression algorithm is.

  If you are using tapes that hold 35GB native, then you can usually
expect to get somewhere between 35-70 GB on a tape.  But sometimes, you
may get even more.  I've seen 120 GB fit on a 35 GB tape!  It all
depends on your data.

John

Charles Bartels wrote:

> Date: Thu, 10 Aug 2000 12:50:55 -0700 (PDT)
> From: Charles Bartels <ceb AT move DOT com>
> To: veritas-bu AT mailman.eng.auburn DOT edu
> <p0432041fb5b865e486d8@[38.31.46.122]>
> <p04320421b5b867cdfb7d@[38.31.46.122]>
> Reply-To: charles AT move DOT com
> Subject: [Veritas-bu] NetBackup tape usage
> 
> Hi,
> 
> I'm running NetBackup with a tape jukebox.  When I look at the media
> list I see the following:
> 
>  id     rl  images   allocated      last updated     den     kbytes  restores
>            vimages   expiration     last read        <------- STATUS ------->
> -----------------------------------------------------------------------------
> DJR892   6      2   08/05/00 22:22:  08/05/00 22:22:     dlt  12795420       0
>                 2   02/07/01 21:22:      N/A
> 
> DJR894   0     26   07/28/00 22:06:  08/09/00 22:09:     dlt  21761349       0
>                16   08/16/00 22:09:      N/A
> 
> DJR897   0     10   08/07/00 22:04:  08/09/00 22:16:     dlt   2021326       0
>                10   08/16/00 22:16:      N/A
> 
> DJR899   6      2   08/05/00 22:08:  08/05/00 22:08:     dlt   5051234       0
>                 2   02/07/01 21:08:      N/A
> 
> DJR902   6      3   07/08/00 22:13:  08/05/00 22:22:     dlt  44499604       0
>                 3   02/07/01 21:22:      N/A         FULL
> 
> DJR904   1     20   06/17/00 22:02:  07/29/00 22:18:     dlt  30258822       1
>                 4   08/12/00 22:18:  06/19/00 09:35:
> 
> DJR908   1     18   06/17/00 22:02:  07/29/00 22:09:     dlt  34380545       0
>                 2   08/12/00 22:09:      N/A
> 
> DJR913   0    155   06/11/00 20:05:  08/07/00 22:04:     dlt  89306394       0
>                11   08/14/00 22:04:      N/A         FULL
> 
> DJR916   6      5   06/10/00 20:02:  08/05/00 22:08:     dlt  35868415       0
>                 5   02/07/01 21:08:      N/A         FULL
> 
> DJR918   5      6   06/10/00 20:02:  08/05/00 22:08:     dlt  13859639       0
>                 6   11/06/00 21:08:      N/A
> 
> DJR920   6      3   06/10/00 20:12:  07/08/00 22:13:     dlt  50211961       0
>                 3   01/10/01 21:13:      N/A         FULL
> 
> =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
> 
> My question is about the "FULL" tapes.  The amount of data on each
> tape varies quite a bit, from 89+ GB down to less than 36GB.  Why the
> huge disparity?
> 
> -C.
> 
> -------------------------------------------------------------------------
>   Charles Bartels <charles AT move DOT com>, Lead Systems Administrator
>      Cendant Corporation / Move.Com @ San Francisco, CA, US
> -------------------------------------------------------------------------
>



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