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

Joanne Neil a écrit :

      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 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


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