[DRBD-user] drbd tranfer limitations (random and sequential acccess) using raw

Lars Ellenberg Lars.Ellenberg at linbit.com
Thu Sep 23 15:09:37 CEST 2004

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


/ 2004-09-23 09:47:48 -0300
\ crsurf:
> > / 2004-09-23 09:01:50 -0300
> > \ crsurf:
> > > Hello list
> > > I?m using drbd in a Gigabit network (crossover cable) and when I
> > > synchronize data (sequential read/write) the tranfer hit to 30~40
> > > Mb/s, but when I make inserts into database (random read/write) that
> > > access drbd device via raw, the transfer rate hit only 5~6 Mb/s.
> > > Exists some way to improve this performance? I increased the
> > > sndbuf-size to 256K, but no such effect. I increase interface MTU to
> > > 9000 and no such effect too. One database process that run in 4 min.
> > > without replication, run in 30 min. with replication. Now I?m trying
> > > using filesystem jfs instead raw to view if the performance will be
> > > improved.
> > > Maybe sync-nice can help us?
> >
> > I am not sure which transfer rate you are talking about.
> > the throughput of your applications, or the resync throughput?
> >
> 
> With resync tha transfer hit 40~50 Mb/s, afer I changed MTU.
> 
> > or the resync throughput while you have resynchronization and
> > applications running concurrently?
> >
> 
> And when I make a insert into database the transfer hit to 4~6 Mb/s,
> without full synchronization, only online synchronization.

which transfer.
sorry, again I don't get you here.

is it that your data base has a write throughput of 6 MB,
or that drbd resync throughput drops to 6 MB while the database is
running?

how do you measure?

and if you are concerned about your database application throughput,
how does it compare to the figures you get when not using drbd?

> > and when you talk about sync-nice, you are using drbd 0.6 ?
> 
> Yes, I?m using 0.6.13
> 
> >
> > maybe you want to use 0.7 instead. it reduces the amount of data
> > transfered to a minimum, thus reducing the time for resynchronization to
> > some one to three minutes, typically.
> 
> Well, I?m already compiled 0.7.4, but my question is: I can use the
> config file of 0.6 in 0.7? And the drbdsetup commands to replicate and
> define primary node are the same?

you have to adopt the conf file, syntax has changed.
should be easy enough.
though, make sure you first read
  upgrade_0.6.x_to_0.7.0.txt and
  upgrade_0.7.0_to_0.7.1.txt

I don't understand what you mean by "commands to replicate".
in general, the interface for 0.7 is the new drbdadm command,
and it has a nice little english manpage that should even be complete.


	Lars Ellenberg

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