[CentOS] DRBD very slow....

[Roman Savelyev]

1. You are hit by Nagel alghoritm (slow TCP response). You can build DRBD 
8.3. In 8.3 "TCP_NODELAY" and "QUICK_RESPONSE" implemented in place.
2. You are hit by DRBD protocol. In most cases, "B" is enought.
3. You are hit by triple barriers. In most cases you are need only one of 
"barrier, flush,  drain" - see documentation, it depens on type of storage 
hardware.

>> The highest speed I can get through that link with drbd is 11 MB/sec
>> (megabytes)
>>
>> But if I copy a 1 gig file over that link I get 110 MB/sec.
>>
>> Why is DRBD so slow?