[dm-devel] deterministic io throughput in multipath

[Hannes Reinecke]

On 12/19/2016 12:50 PM, Muneendra Kumar M wrote:
> Customers using Linux host (mostly RHEL host) using a SAN network for
> block storage, complain the Linux multipath stack is not resilient to
> handle non-deterministic storage network behaviors. This has caused many
> customer move away to non-linux based servers. The intent of the below
> patch and the prevailing issues are given below. With the below design
> we are seeing the Linux multipath stack becoming resilient to such
> network issues. We hope by getting this patch accepted will help in more
> Linux server adoption that use SAN network.
> 
> I have already sent the design details to the community in a different
> mail chain and the details are available in the below link.
> 
> https://www.redhat.com/archives/dm-devel/2016-December/msg00122.html.
> 
> Can you please go through the design and send the comments to us.  
> 
This issue is coming up from time to time.
Standard answer here is that  using 'service-time' as a path selector
_should_ already give you the expected results; namely any path
exhibiting intermediate I/O errors should have a higher latency than any
functional path.
Hence the 'service-time' path selector should switch away from those
paths automatically.

Have you tried this?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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