Quite to the contrary. You usually do want COMPRESSALWAYS when you use
client side compression. The question most often is whether you should
compress at all.

There are (as far as I know) two reasons to use client compression:
1) When you have small disk pools you need to feed them already compressed
data to minimize the load. In this case you do not want COMPRESSALWAYS
because you want to minimize the file size--whether that is compressed, or
uncompressed. But since disks are fairly cheap today I think small disk
pools would be uncommon.

2) Slow network between client and server. This is the vastly more common
reason for client compresion. In this case (nearly always) you want to
minimize the network traffic. If COMPRESSALWAYS=NO the client sends the
server the size of the uncompressed file, then it starts compressing the
file and sending the compressed version. If it sends 1 more byte compressed
than the uncompressed size it says "Compressed file grew" (in effect,
"Whoops" :) and STARTS THE WHOLE FILE AGAIN uncompressed. In other words,
you have *doubled* your network traffic. Not what you were after at all.

So you are probably thinking at this point "So if I have a slow network I
should always use COMPRESSALWAYS.". Not necessarily. If most of your data
was already compressed (gz, ZIP, GIF, or JPEG files for instance), or is
otherwise not amenable to compression then you should not compress it again
because the overhead will cause most of your files to grow--thus increasing
network load. Look at your data. Test and find out. But if you do compress
because of a slow network you should use COMPRESSALWAYS.

Have fun!

Kai.

You are making progress when every mistake you make is a new one.

>Date:    Wed, 10 Apr 2002 16:18:48 +0200
>From:    Daniel Sparrman <daniel.sparrman AT EXIST DOT SE>
>Subject: Re: NetWare, Compression & Slow Backups
>
>Hi
>
>You shouldn't use Compressalways YES. If the file grows, instead of
>shrinks, TSM will keep on compressing the file. This will make the backups
>take a whole lot longer.
>
>Best Regards
>
>Daniel Sparrman
>-----------------------------------
>
>Flemming Hougaard <flhou AT NETVAULTING DOT COM>
>Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
>2002-04-10 14:08
>Please respond to "ADSM: Dist Stor Manager"
>
>
>Hi all
>
>I have read most of the bulletins about NetWare and slow backups - and one
>of those issues there keeps coming up in most of these bulletins, is about
>compression.
>
>I really need the Client compression, but my question is:
> - Should you use the '"COMPRESSALWAYS  YES"? If not why?
>
>Best regards
>
>Flemming Hougaard
>
>