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

crsurf crsurf at
Thu Sep 23 19:18:20 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.

Dont have a way to setup blksize of drbd?
I have the following in the messages log:

Sep 23 13:38:51 SRVSYB01 kernel: drbd0: blksize=512 B
Sep 23 13:39:01 SRVSYB01 kernel: drbd1: blksize=512 B
Sep 23 13:39:07 SRVSYB01 kernel: drbd2: blksize=512 B
Sep 23 13:39:07 SRVSYB01 kernel: drbd3: blksize=512 B

Drbd defining block size to 512 B and database use block size of 2K. I would like to set drbd block size to 2k too.

De:drbd-user-bounces at

Para:drbd-user at


Data:Thu, 23 Sep 2004 14:47:02 +0200

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


> crsurf schrieb:
> >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 think drbd is not the right thing for databases with small block-sizes (my INFORMIX uses 2048 bytes, see separate thread here). My SybaseSQL-Anywhere is running very fast on drbd-replicated-ext3-filesystem. I dont know if you use ASE, but you should try using larger block-sizes (if supported).
> I got an test-prog from an informix-consultant wich runs on local disk in 7 seconds. It takes 8 minutes on drbd-replicated-ext3-filesystem. I am looking forward for an solution...
> Best regards 
> Thomas
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