Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Friday 12 October 2007 12:13:14 Jens Beyer wrote: > Hi, > > we are currently using DRBD very succesfully, mirroring several > TB of data for some time now. (At this point let me thank you > for this really great product :)). > > Now we seek to establish disaster redundancy for some data by > sharing it between two different datacenters preferably using DRBD. > I am currently testing a cluster with nodes separated a few km > using Protocol A/B/C (ping times around 1 ms) with drbd 8.0.6 > successfully. > > To test larger distances with higher latencies we tried to let drbd run > via some TCP-proxies onto a third machine forwarding between the > real drbd hosts (for example using ssh-forwarders, or other userspace > relay-utilities). Using protocol C this works usually very good but due > to rising latencies write access gets slower and slower (up to factor 25 > with a 10 ms delay for each tcp-packet through the proxy). > > To overcome this we tried to use protocol A as it is more important > to us to have some data than to be synchronous. > Using A on a low latency network (LAN) works unproblematic. While > using higher latency setups initial connection setup (like bitmap > exchange) usually works (the connect seems to be more difficult) > we get a lot 'BrokenPipe' states while data is transferred (often > after a few bytes). The latter usually only gets fixed by disconnecting > drbd on one host (starting the cyle all over). > > Sometimes we get > [6214.280107] drbd0: BUG! md_sync_timer expired! Worker calls > drbd_md_sync(). > > while usually drbd just constantly tries to reconnect: > [6220.255205] drbd0: sock was shut down by peer > [6220.255217] drbd0: conn( WFReportParams -> BrokenPipe ) > [6220.255230] drbd0: short read expecting header on sock: r=0 > [6220.255236] drbd0: My msock connect got accepted onto peer's sock! > [6226.251812] drbd0: tl_clear() > [6226.251818] drbd0: Connection closed > [6226.251829] drbd0: conn( BrokenPipe -> Unconnected ) > [6226.251841] drbd0: conn( Unconnected -> WFConnection ) > [6226.295766] drbd0: conn( WFConnection -> WFReportParams ) > [6226.296156] drbd0: sock was shut down by peer > [6226.296164] drbd0: conn( WFReportParams -> BrokenPipe ) > [6226.296172] drbd0: short read expecting header on sock: r=0 > [6226.296178] drbd0: My msock connect got accepted onto peer's sock! > [6232.288608] drbd0: tl_clear() > (( repeating until drbd disconnect r0 )) > > I was wondering if someone has experience running DRBD on long distances or > high latencies link with ping times up to tens of ms possibly with > protocoll A? > > Any hints or tips to tune such setups are welcome. > Hi Jens, Interesting... We (in the sense of LINBIT) have just developed a DRBD-proxy tailored for especially this purpose. We just have not yet told anybody about it. Maybe you want to contact us in that regard... -Phil -- : Dipl-Ing Philipp Reisner Tel +43-1-8178292-50 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Vivenotgasse 48, 1120 Vienna, Austria http://www.linbit.com :