[pve-devel] backup : add pigz compressor

[Dietmar Maurer]

> I ran a quick, informal "benchmark" to compare lzo, gzip, pigz, and
> uncompressed backups of a modest 8GB VM on a host with 8 cores, all
> currently at 100% from guest usage. 
> 
> None: 50 seconds, 199MB/s, output 963MB
> pigz: 20 seconds, 453MB/s, output 266MB
> gzip: 57 seconds, 150MB/s, output 254MB
> lzop:   9 seconds, 954MB/s, output 362MB
> 
> These results demonstrate a clear trade-off between speed and
> compression with gzip and lzo. However, pigz offers gzip's compression
> ratio at only a modest bump in the time it took to compress it. 
> 
> I'm not saying pigz is for everybody or all scenarios or deployments,
> but it has worked well for mine. 

But pigz needs all you CPU power do be that fast! If you have running VMs, 
it will be as slow as normal gzip, or it will massively slow down the VMs.
I am really afraid this will trigger many support calls ...