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Re: [dm-devel] [PATCH] [RFC] multipath: change the DEFAULT_MINIO for the request based multipath



On 01/19/2011 10:30 PM, Malahal Naineni wrote:
> The value of 1000 is good for bio based multipath. Seen 50% increase in
> I/O ops by setting it to 1 in request based multipath configuration.
> This patch would give poor performance for people still using the bio
> based multipath!
> 
> Is it possible to detect request based multipath and change only for
> those configurations?
> 
> diff -r e504a50b0db5 -r 91d6dae7d882 libmultipath/defaults.h
> --- a/libmultipath/defaults.h	Wed Jan 19 13:16:40 2011 -0800
> +++ b/libmultipath/defaults.h	Wed Jan 19 13:29:52 2011 -0800
> @@ -5,7 +5,7 @@
>  #define DEFAULT_ALIAS_PREFIX	"mpath"
>  #define DEFAULT_FEATURES	"0"
>  #define DEFAULT_HWHANDLER	"0"
> -#define DEFAULT_MINIO		1000
> +#define DEFAULT_MINIO		1
>  #define DEFAULT_PGPOLICY       FAILOVER
>  #define DEFAULT_FAILBACK       -FAILBACK_MANUAL
>  #define DEFAULT_RR_WEIGHT      RR_WEIGHT_NONE
> 
Heh, that was the main reason for using request-based multipathing :-)

So yes, changing the behaviour is a good idea. But we should equally
be able to detect if request-based multipathing is present; maybe
we can key off the version number of dm-multipath?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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