[dm-devel] Re: Technical information requested on MultiPath module of Linux

[Christophe Varoqui]

Joanne Neil a écrit :
> Hello,
>
>       I was in search of technical details on MultiPath module of Linux. I found
> the excellent page of  christophe. I apologize for sending the email to you
> directly. Can I know:
>
> a. Which will be the right email forum to send technical/development questions
> on MultiPath for Linux?
>
>   
dm-devel at redhat.com
> b. I was looking at Linux 2.6.11 MultiPath code and found EMC CX/AX
> specific code. This is where I am most interested in. Does it require that
> a storage vendor has to implement specific hooks for the generic MultiPath
> code to work with their product in Linux?. If yes, can I be pointed link or
> references or document on what a storage vendor has to implement to
> have their storage work on Linux.
>
>   
I guess you refer to "hardware handlers" modules. Those are needed only 
if special host-initiated action is needed for the storage hardware to 
activate failback paths.

This is often the case with asymmetric arrays.
> c. From what I have read, the MultiPath architecture has changed from
> Linux 2.4 and Linux 2.6. Is this correct?. And the device mapper architecture
> was introduced in Linux 2.6.
>
>   
The DM multipath driver is lk2.6 only. The MD multipath driver was 
available in lk2.4, and is still maintained in lk2.6. The 
multipath-tools interface the DM framework only.
> d. Will Linux 2.6 MultiPath code be applicable to Linux 2.4?
>
>   
There is no plan for userspace tools to support lk2.4 (pre-sysfs 
kernels, pre-kevents).
Hardware handlers use a "lk2.6 DM" specific API.
> Appreciate any help
>
> Regards
> Joanne
>