[DRBD-user] DRBD Transport Latency

Lars Ellenberg Lars.Ellenberg at linbit.com
Tue Jan 30 14:08:07 CET 2007


/ 2007-01-29 10:30:52 +0100
\ H.D.:
> Hello,
> 
> I'd like replicate a DBMS (PostgreSQL) under heavy OLTP workload with protocol C. By heavy I mean > 1500 
> transactions per second, which results in at least as many fsyncs.
> 
> I've used DRBD a while, but in way smaller setups, where performance was secondary.
> 
> The hardware I'm planing to run this on has not been delivered yet, so I can't just test it. My question now is 
> whether (trunked) gigabit ethernet can delivery the short round trip times required for this application at all 
> and if DRBD can use other transports such as Infiniband?

DRBD is happy to use any IPv4 based network you give it.
(or probably v6, but I think our config
tools do not support the v6 syntax yet)

also note that rtt in LAN is usually orders of magnitude
less than average seek time/fsync time of storage.
also in a dedicated fo for over 20km,
rtt might be in the order of one digit ms, iirc.

drbd8 should give some improvements regarding latency, too.

-- 
: Lars Ellenberg                            Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
: Vivenotgasse 48, A-1120 Vienna/Europe    http://www.linbit.com :
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