[DRBD-user] tuning DRBD

[Ben]

Does anybody have any advice for tuning DRBD 0.7? I'm not seeing much  
out there except for some un-explained bullet points for a hacked  
version for use with OpenSSI, and I don't know how much of that  
advice is due to assumptions that are only true for OpenSSI. Some  
specific questions I have are:

1. What are the tradeoffs with changing al-extents?
2. Can I eck out more throughput by increasing sndbuf-size? Does that  
increase my write latency when using Protocol C?
3. What's a reasonable formula for determining max-buffers? Does  
increasing them imply I should increase something else too?
4. Does anybody know if the Areca raid cards like high or low unplug- 
watermark settings?
5. Does decreasing max-epoch-size reduce my write latency?

Does anybody have any experience playing with the schedulers in the  
2.6 kernel?