Re: [Veritas-vx] Age old question - PowerPath/DMP clarification ...

Thu, 28 Sep 2006 16:58:46 -0700

Hi Sanjay,
 
What we have heard is that DMP will fail to re-enable a failed path whereas
PowerPath does.  So when connecting to Clariions this becomes an issue
because Clarrions offer active/passive SAN connection.  This however is
not an issue with Symmetrixes.  I have also heard from after version 4 and beyond,
this issue about DMP not re-enabling the failed path is not an issue anymore
and this has been fixed.  Can somebody at Veritas or somebody who has
intimate knowledge on this subject confirm this, please?
[Thomas] This is not an issue in 4.1 MP1. DMP 4.1 will detect that a path is back online and will automatically failback to it.
You shouldn't have any probelm running DMP with Clariion arrays as long as you have the right ASL / APM loaded on your host.
 
____________
 
Thomas Cornely
Sr. Product Manager - Dynamic Multi-Pathing (DMP)
Veritas Storage Foundation for UNIX
Data Center Management Group (DCMG)
Symantec Corporation
 
 
 
 
 

From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sanjay Gowda
Sent: Wednesday, September 27, 2006 4:32 PM
To: veritas-vx@mailman.eng.auburn.edu
Subject: [Veritas-vx] Age old question - PowerPath/DMP clarification ...

All,
 
As usual I have to turn to the good folks on this list to help me out here.
I needed a couple of answers concerning PowerPath v/s DMP.
 
We have installed Veritas 4.1 MP1 on all of our boxes.  And since it comes with
DMP, we are happy with the way it performs and handles failover.
 
However recently we purchased a whole bunch of Symmetrixes and Clariions
and hence alongwith that our group got a huge discount on PowerPath.  Don't ask.
As usual many of these decisions are done without every consulting the very
people who administer the servers.  And hence the debate has risen whether
to install PowerPath after disabling DMP.
 
What we have heard is that DMP will fail to re-enable a failed path whereas
PowerPath does.  So when connecting to Clariions this becomes an issue
because Clarrions offer active/passive SAN connection.  This however is
not an issue with Symmetrixes.  I have also heard from after version 4 and beyond,
this issue about DMP not re-enabling the failed path is not an issue anymore
and this has been fixed.  Can somebody at Veritas or somebody who has
intimate knowledge on this subject confirm this, please?
 
The Storage/SAN team is adamant and are saying, look, if you want 99.9% and above
availability of your SAN disks, you should install PowerPath. 
 
Another question we have is, we have heard that performance of DMP on boxes
with more than 2 HBAs is many times better than PowerPath.  If anybody has
any benchmarks that they would like to share, we would really appreciate it.
 
Thank you.
 
- Sanjay

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