[DRBD-user] Protocol A vs Protocol C performance issue?

Digimer lists at alteeve.ca
Tue Oct 20 18:23:37 CEST 2015

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 20/10/15 11:47 AM, Lionel Sausin wrote:
> Le 20/10/2015 17:30, Joeri Casteels a écrit :
>>> Protocol A an async, C is sync. So you're probably hitting the network
>>> limit on C.
>> I don’t think so since it has a direct 20G trunk in-between with perf
>> i get 19.6Gbit/s on single threat. With A (async when i monitor the
>> network it also hits 2x the network speed as C does)
> "sync" means the round-trip time (down to the remote disks) is what
> counts, not the bandwidth.


In protocol C, the write is not completed until it has hit persistent
storage on both nodes. I guessed it was your network, but it could also
be your disk.

Also, use 'fio', not 'dd' to test performance.

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