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drbd-user: [DRBD-user] Performance issue

[DRBD-user] Performance issue

From: Julien Escario <escario_at_nospam>
Date: Fri May 14 2010 - 09:09:50 GMT
To: drbd-user@lists.linbit.com

Hello,
I'm trying to optimize write performances on a primary/primary drbd cluster.

The nodes are connected directly with a dedicated gigabit network.

To get rid of filesystem perfs, I'm adressing the drbd ressource directly.

Here's what dd gives me (I'm using one big chuck to get rid of latency) :

# dd if=/dev/zero of=/dev/drbd0 bs=512M count=1 oflag=direct
1+0 enregistrements lus
1+0 enregistrements écrits
536870912 octets (537 MB) copiés, 30,3065 seconde, 17,7 MB/s

Now, I disconnect the ressource :
# drbdadm disconnect r0

And I have very better perfs :
# dd if=/dev/zero of=/dev/drbd0 bs=512M count=1 oflag=direct
1+0 enregistrements lus
1+0 enregistrements écrits
536870912 octets (537 MB) copiés, 8,6145 seconde, 62,3 MB/s

When syncing, I get :
finish: 3:07:23 speed: 61,240 (55,320) K/sec

Which seems around the real performance.

The version is :
version: 8.0.16 (api:86/proto:86)

Do you have any clue about what is giving me this 3.5 factor ?

What other information can I give you ?

Thanks for your help,
Julien Escario
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