Re: Performance of packet writing: Blocksize matters

Johannes Niess wrote:
> The classical mkisofs route works as expected. Feeding the packet driver with 
> 4k blocks (mbuffer -s 4096) results in the full advertised 8x DVD writing 
> speed:
> 
> tar -cvM -L4500000 -f - /mnt/data/backup/debian-2005-02-06.tar.gz /mnt/data/backup/snapshots/daily.0/ |
> mbuffer -m 1000k -s4096  -P 10 > /dev/pktcdvd/dvdrw
> 
> Without the -s 4096 option I get the same low performance behavior. I also 
> tried different buffer sizes in the kernel module and the experimental write 
> caching.

I have no idea what mbuffer is or what it is doing, but if you just dd a 
file to the pktcdvd device, you can use any block size you want and it 
works fine because the pktcdvd driver merges the small writes into full 
packets.