[DRBD-user] poor performance - re-partitioning suggested

Lars Ellenberg lars.ellenberg at linbit.com
Tue Sep 11 10:35:04 CEST 2012

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


On Tue, Sep 11, 2012 at 09:40:35AM +0200, Raphaël LOUIS wrote:
> Hello DRBD-user group,
> 
>  
> 
> I have an optimization problem when formatting the filesystem on a drbd
> partition;
> 
>  
> 
> When I type the following command :
> 
>  
> 
> mkfs.ext4 -m 0 /dev/drbd0
> 
>  
> 
> I get this warning :
> 
> L'alignement de /dev/drbd0 est décalé de 3072 octets.
> 
> Cela peut induire de très mauvaises performances, il est suggéré de
> (re)-partitionner.
> 
>  
> 
> English translation :

For future reference, please do not translate localized error messages
yourself.  Don't.  Rather do: export LC_ALL=C LANG=C


> /dev/drbd0 alignment is offset by 3072 bytes.
> 
> This may result in very poor performance, (re)-partitioning suggested.

Did you check this "may" for relevance in your setup?
Did you actually experience a measurable or even relevant performance
degradation? Against what baseline? For what usage pattern?


> This drbd resource is configured on a soft raid  (disk /dev/md0) of a 2 TB
> partition.

Then that same soft raid is already "misaligned".
Or possibly the partitions it consists of.

DRBD does not change the alignment of the block device below it.

> I have another drbd resource configured on the same server with the same
> configuration but a 20 GB partition and I don't get the warning for this
> one.
> 
>  
> 
> I took an afternoon on this, but I couldn't fix it.
> 
> Does somebody have any idea ?


-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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