is it possible to use multipathd with vxvm, and not vxdmp?

[casualcramp]

Hello,

I'm using rhel 5.5 64bit. I would like to know about the possibility of using vxvm with native Linux multipathd instead of the bundled vxdmp pathing software. Is this possible, or recommended? why or why not?

Cheers,

Marc

[Marianne]

Seems it is possible:

Hardware Compatibility List for Veritas Storage Foundation 

p.2:

NOTE: The DMP OS native stack support feature has been released through add-on patch on 5.1 release. DMP OS native stack support feature would allow new/existing non-root OS native volume groups or file systems to operate over DMP devices. This feature is available for ZFS on Solaris 10 (SPARC, and X64), LVM on AIX 5.3, 6.1, and 7.1, LVM on HP-UX 11iv3, and LVM on Linux RHEL5, RHEL6, SLES 10, and SLES 11. For DMP OS native stack support patch information on 5.1 release, see <https://sort.symantec.com/patches> . On 5.1SP1 release, the DMP OS native stack feature is supported without addtional patch.

[casualcramp]

Thanks for your reply Marianne. But this sounds like vxdmp supporting LVM, but I'm looking for linux multipathd supporting vxvm.

[mikebounds]

My guess is that this is not supported, but you may need to log a Support call to get this clarified for sure, unless someone from Support/Engineering reads this thread.  On the HCL (http://www.symantec.com/business/support/resources/sites/BUSINESS/content/live/TECHNICAL_SOLUTION/74000/TECH74012/en_US/330441.pdf) in the "Disk Array" section (at the beginning) it says:

For information on Storage Foundation DMP co-existence with OS native multi-pathing drivers such as MPIO on AIX and MPxIO on Solaris, see Technote <http://entsupport.symantec.com/docs/4736>

and this technote says:

Storage Foundation does not support MPxIO on non-sun storage arrays.

but this is Solairs only and says nothing about AIX, let alone any other O/Ss.  In the HCL, again in the "Disk Arrays" section, under the "AIX" section it says:

Array vendor ODM definitions are requred  with MPIO disabled for DMP to manage multipathing.  For detail, see <http://seer.entsupport.symantec.com/docs/341102.htm>

But there is nothing under Linux sections.

So in the absence of any information in the SF releases notes  or the HCL about support with Linux Multipathing I would say it is not Supported (note Solaris releases notes has a "Veritas Volume Manager coexistence with SVM and ZFS" section, although this doesnt' mention disk multipathing, but Linux release notes have no equivalent section)

Note, although it is not Supported it may work - I had a customer (I am a Consultant) who used Solaris MPxIO with a NON-Solaris Array for a year, before Symantec Support pointed them to the above technote which says it is not supported, so then customer had to switch to DMP.

Mike

[joseph_dangelo]

Marc,

I have customers who have asked to have this configuration implemented with MPxIO.  I have not personally tried this with mpathd however.  DMP will work with native volume managers and TPD multipath utilities (powerpath for example), however to use VxVM with mpathd would most likely require suppressing the devices VxDMP's view using the command "vxdmpadm exclude all"

https://sort.symantec.com/public/documents/sfha/5.1sp1pr2/linux/productguides/pdf/vxvm_admin_51sp1pr...

Take a look at pages 184-185.

This however would not be a recommended configuration as DMP will provide substantially more array based information and I/O path options with its sub-path failover functionality. Essentially DMP is able to not only identify a failed path but it can quickly determine any and all subsequent paths that would all be effected the same failure.  Therefore it need not test I/O down those paths.  Imagine a system with 2 HBA ports x 2 Switches by 8 Array controllers ports (A/A or A/P).  You could have upwards of 16 paths to a device.  If a single switch fails, native multipath drives will check all 8 paths associated with that switch.  Whereas DMP acknowledges a sub-path which would allow for a seamless transition to an active path with testing additional failed links.   

Hope this helps,

Joe D

[Marianne]

Marc - if I may ask - what is the reason for your query?

What exactly do you need to use without vxdmp?

[TonyGriffiths · Accepted solution]

Hi

Its not supported to use VxVM/SF with native linux multipathing as a multipathing solution, there is no interaction between DMP layer and LinuxDM.

If you have the SF stack, you will have DMP functionaility.

Is there a reason/problem why DMP cannot be used ?

thanks

tony