ADSM-L

Re: ADSM 9840 & Compression

2015-10-04 17:33:43
Subject: Re: ADSM 9840 & Compression
From: Angelo DeAngelis [mailto:Angelo_DeAngelis AT TIVOLI DOT COM]
To: ADSM-L AT VM.MARIST DOT EDU
This my friends is the best explanation of the situation.




"Prather, Wanda" <Wanda.Prather AT JHUAPL DOT EDU> on 02/14/2000 12:48:30 PM

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

To:   ADSM-L AT VM.MARIST DOT EDU
cc:    (bcc: Angelo DeAngelis/Tivoli Systems)
Subject:  Re: ADSM 9840 & Compression



We are running 9840's, converting all our old data from DLT7000.

I'm getting exactly the same results on the 9840's that I saw on the
DLT7000's.

If I take a DLT7000 tape that filled at native capacity (35 GB), then I know
it was already-compressed data.  A MOVE DATA to a 9840 ends up filling the
9840 at 20 GB.

If I take a DLT7000 that filled at 70-100GB, I know the data was not
compressed to start with, and a MOVE DATA to a 9840 ends up filling the 9840
at 70-80GB.

So it's working about as expected.  If the data is compressed by the
software, it isn't going to compress much more in the hardware - you'll get
an additional 10% if you're lucky.

Remember that even if you don't have COMPRESSION ON in the ADSM client, some
types of data are already naturally compressed - Windows machines with
stacking or compression on in the disk file system; Microsoft Exchange
files, SQL data base files, some types of graphics files such as .tif and
.gif files will compress little if at all.

So I find the results on tape vary a whole lot.

************************************************************************
Wanda Prather
The Johns Hopkins Applied Physics Lab
443-778-8769
wanda_prather AT jhuapl DOT edu

"Intelligence has much less practical application than you'd think" -
Scott Adams/Dilbert
************************************************************************





> -----Original Message-----
> From: Long, Matt [SMTP:Matt.Long AT MARRIOTT DOT COM]
> Sent: Monday, February 14, 2000 9:45 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: ADSM 9840 & Compression
>
> John,
>
>         We are also seeing some bizzare compression rates with the 9840.
> Some of our tapes are reporting over 80Gig of data. I don't know if this
> is
> a bug or what. We are using ADSM attached to an AIX RS6000.  Thanks
>
> Matt Long
> Systems Administration
> Marriott International
>
>
> -----Original Message-----
> From: Doherty, John (ANFIS) [mailto:jdohe1 AT ANFIS.CO DOT UK]
> Sent: Monday, February 14, 2000 5:46 AM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: ADSM 9840 & Compression
>
>
> ADSM ver 3 rel 1 level 2.20, device class defined as follows
>
>  <<...>>
>
> What level of the ADSM server are you running?
>
> Have you specified "9840C" as the format when configuring your device
> class?
> (Q
> DEVCLASS)
>
>
> regards,
>
> Stuart Robertson
> Unitech Open Systems Scotland
>
>
> > John Doherty. Tel:   +44   (0)   141 275 7793
> >               Fax:  +44   (0)   141 275 9199
> >               Email: JDohe1 AT Anfis.co DOT uk
> >
> >       Technical Specialist, Storage Management L02S
> >
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