Re: Performance of packet writing: Blocksize matters

On Friday 15 December 2006 23:24, Johannes Niess wrote:
> Did I forget something stupid or does this also occur on your hardware? All
> you need is a DVD+RW medium without valuable data. You can savely abort
> (^C) when it takes too much time.

Just to confirm and add to the statistics - I see this behaviour too but the 
performance through pktcdvd is much lower even for the 32768B blocks; drive 
is NEC ND-4570, kernel is stock 2.6.19.

With 8x DVD+RW media:

# dd if=/dev/zero of=/dev/hda bs=32768 count=25000
25000+0 records in
25000+0 records out
819200000 bytes (819 MB) copied, 96.3903 seconds, 8.5 MB/s
# dd if=/dev/zero of=/dev/hda bs=32769 count=25000
25000+0 records in
25000+0 records out
819225000 bytes (819 MB) copied, 772.428 seconds, 1.1 MB/s
# pktsetup dvdrw /dev/hda
# dd if=/dev/zero of=/dev/pktcdvd/dvdrw bs=32768 count=25000
25000+0 records in
25000+0 records out
819200000 bytes (819 MB) copied, 527.97 seconds, 1.6 MB/s
# dd if=/dev/zero of=/dev/pktcdvd/dvdrw bs=32769 count=25000
25000+0 records in
25000+0 records out
819225000 bytes (819 MB) copied, 830.979 seconds, 986 kB/s
# pktsetup -d dvdrw

I also tried it with 5x DVD-RAM media to see what would happen:

sh-3.1# dd if=/dev/zero of=/dev/hda bs=32768 count=25000
25000+0 records in
25000+0 records out
819200000 bytes (819 MB) copied, 185.128 seconds, 4.4 MB/s
sh-3.1# dd if=/dev/zero of=/dev/hda bs=32769 count=25000
25000+0 records in
25000+0 records out
819225000 bytes (819 MB) copied, 974.509 seconds, 841 kB/s

Stephen