[DRBD-user] drbdmanage pure client write speed

[Julien Escario]

Le 24/09/2018 à 16:36, Brice CHAPPE a écrit :
> Hi mailing !
> 
>  
> 
> I have three nodes drbdmanage cluster.
> 
> Two nodes work as storage backend (S1/S2).
> 
> One node as satellite pure client (for future nova usage)
> 
> I work on 20GB/s LACP network between storage backends and satellite pure client
> node
> 
>  
> 
> So, when I bench on local drbd on storage node with two nodes connected with :
> 
> dd if=/dev/zero of=/dev/drbd104 bs=1M count=512 oflag=direct
> 
> I have almost 680 MB/s => It is ok for me
> 
>  
> 
> After I assign the resource to the satellite node.
> 
> I try the same thing on it :
> 
> dd if=/dev/zero of=/dev/drbd104 bs=1M count=512 oflag=direct
> 
> I get 420MB/s => why ?

You're experiencing latency ;-)
Check using scripts here :
https://docs.linbit.com/docs/users-guide-9.0/#p-performance

With a little maths, you'll understand what's happening (consider your 1M block
size and retry with smaller I/O).

Best regards,
Julien