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RE: [dm-devel] [ANNOUNCE] multipath-tools-0.1.4



Does the multipath tools provide policies for during failover as well?

> -----Original Message-----
> From: dm-devel-bounces redhat com 
> [mailto:dm-devel-bounces redhat com]On
> Behalf Of christophe varoqui free fr
> Sent: Wednesday, March 17, 2004 9:22 AM
> To: device-mapper development; Lars Marowsky-Bree
> Cc: device-mapper development
> Subject: Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.4
> 
> 
> Selon Lars Marowsky-Bree <lmb suse de>:
> > 
> > Hi, I'm kind of unsure. What does multipath-tools now mean 
> for LVM2 and
> > EVMS2's multipath support, given a distributors perspective? ;-)
> > 
> > Do the multipath tools handle all multipath scenarios we 
> may encounter
> > (or at least are supposed to), and will LVM2 and EVMS2 
> stack cleanly on
> > top of it?
> > 
> the multipath-tools design is policy agnostic :
> 
> the multipath configuration tool has 2 sets of policies :
> 
> * paths grouping policies (drive the number and content of 
> priority groups) :
> 
>   * one priority group (full IO spreading)
>   * one priority group per path (failover, only one path 
> active at a time)
>   * one priority group by serial number (spread IO to all 
> paths through a
> controler in a pair)
>   * one group for active paths, one group for failed paths 
> (for controlers that
> disable their fallback paths)
> 
> * UUID fetching policies (methods to get the UUID that will 
> be used to coalesce
> paths into multipaths)
> 
>   * SCSI INQ EVPD page 0x83 : LU WWID
> 
> the multipathd daemon has only one set of policies : methods 
> to determine if a
> path is up or down.
> 
> * do a SCSI TUR
> * do a test IO
> 
> policies can be added to fit every needs.
> policies are selected based on the SCSI strings tuple (vendor/product)
> 
> hope it helps,
> cvaroqui 
> 
> 
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