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

Lars Ellenberg Lars.Ellenberg at linbit.com
Thu Sep 23 14:26:04 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 09:01:50 -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?

or the resync throughput while you have resynchronization and
applications running concurrently?

and when you talk about sync-nice, you are using drbd 0.6 ?

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.

	lge



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