Networker

Re: [Networker] tape drive hardware compression a bad thing?

2003-01-29 09:49:27
Subject: Re: [Networker] tape drive hardware compression a bad thing?
From: "Garcia, Jose" <Jose_Garcia AT BMC DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Wed, 29 Jan 2003 08:49:17 -0600
I've seen some database backup utilities with better compression ratios than
hardware compression. As I've always understood compression, if the data is
already compressed on the client, it will not get compressed on the tape. In
fact tapes written by some of our servers that compress their data only fill
the tape to native capacity.

This is the only reason I can think of for suggesting software compression.

Regards
-Jose

-----Original Message-----
From: Sean Beeg [mailto:sean.t.beeg AT VERIZON DOT COM]
Sent: Wednesday, January 29, 2003 8:35 AM
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: Re: [Networker] tape drive hardware compression a bad thing?


Jim et al,

I have also heard quite the opposite, especially as stated by the expert
from a well known VAR who assisted us with our L180/DLT7000 library setup
back in 2000.
He did specifically say not to use software compression but that hardware
compression on a DLT7000 is the way to go.
In practice, I've always tried to go with hardware compression but have
seen peformance issues with software compression.
What does it matter if the drive compresses the data stream and then writes
it to tape?  I suppose the only issue there would be if Legato was
controlling the tape drive instead of allowing your device drive to handle
it for you.
And I know for a fact on DLT7k that legato handles it well.

Cheers,

-Sean
Systems Engineer
Verizon





"Stan Horwitz" <stan AT TEMPLE DOT EDU>@LISTMAIL.TEMPLE.EDU> on 01/29/2003
08:23:01 AM

Please respond to "Legato NetWorker discussion"
       <NETWORKER AT LISTMAIL.TEMPLE DOT EDU>; Please respond to "Stan Horwitz"
       <stan AT TEMPLE DOT EDU>

Sent by:    "Legato NetWorker discussion" <NETWORKER AT LISTMAIL.TEMPLE DOT EDU>


To:    NETWORKER AT LISTMAIL.TEMPLE DOT EDU
cc:
Subject:    Re: [Networker] tape drive hardware compression a bad thing?


On Wed, 29 Jan 2003, Jim Lane wrote:
> I recently had a contractor/consultant onsite to review my Networker
> setup. among other things he insisted that using hardware compression on
> a tape library is a "bad thing". the closest thing to an explanation I
> ever heard was that it might cause data loss somehow and that Legato
> wouldn't help me if it did. since contractors have a better relationship
> with management than I do he just called STK onsite and had them turn
> compression off on my 9710. I'm wondering if anybody out there has ever
> heard anything like this before? does anybody have any experience of the
> possible effects, on either reliability or performance, of tape hardware
> compression?

I have heard the exact opposite from a wide range of sources, including
when I attended Legato training and our hardware manufacturer's technical
consultants.

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