Networker

Re: [Networker] Calculating optimal paralelism and target session values

2004-01-20 07:25:00
Subject: Re: [Networker] Calculating optimal paralelism and target session values
From: "Tarjei T. Jensen" <Tarjei.Jensen AT AKERKVAERNER DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 20 Jan 2004 13:24:59 +0100
Davina Treiber  wrote:
> Personally I never use client side compression except when backing up
> over a very slow link (i.e. slower than token ring). Using
> client side compression and then writing to a compressed device can make
> the data on
> tape larger than using just one type of compression.

To repeat myself; the problem with the DLT4000 is data underrun. It runs out of 
data to write to the tape. The data dries out during compression of text or 
text like data. The interface is not able to deliver uncompressed data fast 
enough. If you want to be able to stream a DLT4000 at all times, you must turn 
off hardware compression.

The DLT7000 solves this problem by having a larger buffer and if neccessary; 
writing data before it is completely compressed. It tries to keep the tape 
streaming regardless. It means that less get written to the tape.


greetings,



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