a few questions about kafka usage

["Yu, Libo " <li...@citi.com>]

Hi,

Question 1: If I changed server.properties and added or modified the following line:
                          log.flush.intervals.ms.per.topic=topic1:1000, topic2:3000
                      Do I have to restart the server to pick up the change?

Question 2: I have three machines with one broker on each of them. 100 producers are
                      running on the same three machines. The producers will produce 1M
                      20k-byte messages altogether. The batch size is fixed at 100. For 5 topics
                      each with five partitions, the performance is extremely good. For each topic,
                     30k messages were produced per second . For 10 topics with 10 partitions,
                     the performance is really bad. For each topic, 400 messages were produced
                     per second. The gap is so huge. Any insight on what may cause the difference?

Regards,

Libo