Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi, >> Now, how do i "debug" sync? :-) > > your writes are being delayed. What "bug" are you trying to find? Well, without drbd in use the writes on the very same - sdb-device - volume_group - lvm_volume are not being delayed. And currently im looking at drbd as a possible cause. It must not necessarily be a bug :-) > What does top have to say about CPU utilization (iowait)? top shows 1-2 core(s) of eight total at around 95-100% wait while the aforementioned dd is running, the other six are 90-95% idle. That got me thinking about the cpu-affinity of the drbd-threads and i looked at the worker drbd_worker: ### $ taskset -p 3953 pid 3953's current affinity mask: 40 ### For some reason only one core is being assigned, even though 8 are available. That was the case on both nodes. I tried setting cpu_mask ff; in the config on both nodes. which worked fine: ### $ taskset -c -p 3953 pid 4385's current affinity list: 0-7 ### But it only worked for the drbd_worker and drbd_asender, not for the drbd_receiver. Is that the desired behaviour? Sadly the write-delay-behaviour has not changed after setting this, doing 'adjust' and running a dd+sync. Any hints here? > Is the network link congested? No, the network link is performing fine syncing at 25MB/s without any problems. > How is the RTT developing? I guess we're talking round-trip-time? If so, there is only a single switch inbetween the two servers which also shows no problems or any kind of error message (its managable, with syslog etc.).