On 2/10/2010 10:36 AM, Sean M Clark wrote:
> On 2010Feb10 8:50 AM, Steve Polyack wrote:
>    
>> On 2/10/2010 8:16 AM, Petar Bogdanovic wrote:
>>      
>>>> I want use bzip2 to compress my file, because I thing bzip2 is more
>>>> efficient...
>>>>
>>>>          
>>> Really?
>>>        
> [...]
>    
>>> 255526 bytes less while six times slower..
>>>
>>>        
>> This is extremely dependent on the contents of foo.iso.  I don't think
>> its a good test because you are only seeing 10% compression either way.
>> There is a good chance that much of the data within your ISO is already
>> compressed.  When using data which is typically more compressible (text
>> and other data that is not already compressed), the resulting size of
>> something compressed with bzip2 can be much smaller than when compressed
>> using gzip.  It's true that it is much slower, but if he's talking about
>> it being more efficient in terms of disk space used, then he is correct.
>>      
> xz/lzma is another consideration.  At moderate compression levels, lzma
> seems to be about the same or slightly faster than bzip2 with a little
> better compression.  At lower compression levels it seems like it's
> about as fast as gzip while compressing noticeably farther - at least
> in the small amount of testing I've done so far with the "xz"
> implementation of lzma compression.
>
> (The small amount of testing I've done so far suggests to me that xz
> with a compression level of 1 runs about as fast as gzip4 with
> compression at or better than gzip7, approaching bzip2 for some types of
> files.  Cranking up to xz 6 or 7 runs a bit faster than bzip2 default
> but tends to give better compression.)
>
>    
On the other side of the spectrum, LZO/LZO2 compression is available 
which greatly favors compression speed while still providing a decent 
compression ratio.  I'd like to see these algorithms make their way into 
Bacula, but their doesn't seem to be much interest in doing so.  I 
suppose its understandable, as GZIP is fairly flexible.

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