Storage Foundation for Windows (SFW) DMP Device Specific Module (DSM) returns a bogus path during a path failover operation

Article:TECH75004  |  Created: 2009-01-29  |  Updated: 2012-06-23  |  Article URL http://www.symantec.com/docs/TECH75004
Article Type
Technical Solution

Product(s)

Environment

Languages

Problem



Storage Foundation for Windows (SFW) DMP Device Specific Module (DSM) returns a bogus path during a path failover operation

If a path fails or is removed during IO, DMP DSM may return a bogus path which causes IO to the Volume to fail.
 


Error



Log Name: System
Source: mpio
Date: DD/MM/YYYY HH:MM:SS
Event ID: 33
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: HOSTNAME
Description:
DSM NAME returned a bogus Path to \Device\MPIODisk5.


Environment



SFW with DMP

  • There are disks within the same array which have a different number of paths.
  • There are disks within the same array which have some paths in common, but not all paths in common.

For example:
* Harddisk1 has 2 paths to the array, denoted 1-0-0, 2-0-0.
* Harddisk2 has 4 paths to the array, denoted 1-0-0, 2-0-0, 1-0-1, 2-0-1.
 

In this case, harddisk1 and harddisk2 share 2 paths, but Harddisk2 also has paths that are not common. 


Cause



DMP DSM uses the DsmInvalidatePath API from the Microsoft MPIO framework.  In the event of a path failure, a surviving path is returned without knowledge of which specific disks have a path that is being removed.  If the disks therefore share some paths and not other paths, there is a possibility that a disk may be given a path that does not belong to it.
 


Solution



In order to avoid this issue, the following conditions should be met:
  • If a disk shares any paths with another disk in the same array, they must share exactly the same paths.
  • If a disk does not share a path with a disk in the same array, then they must not share any paths.

That is, they must share all paths, or no paths.

Please Note:
In configurations utizing EMC Symmetrix arrays, it is possible to have ACLX (Access Control Logix) and/or GateKeeper devices that are zoned down many (or all) configured paths and may overstep the path boundaries by using paths from several different disk subsets. In these configurations, there is the possibility that during a path failure, MPIO requests an available path the ACLX/GateKeeper device which could result in the Bogus path error being reported:
 
Example:
ACLX/Gatekeeper Devices: Paths 1-8
Harddisks1-5: Paths 1-4
Harddisks6-10: Paths 5-10
 
In this scenario, if Path 1 failed and MPIO requested an available failover path from an ACLX/GateKeeper device, it can choose Paths 2-8. If it chooses Path 6, then all disks with failed I/O on Path 1 will move to Path 6. In this case, since Harddisks 1-5 do NOT have Path 6 configured, this would result in failed I/O and the Bogus Path message being logged.
 
Since ACLX/GateKeeper devices should be excluded from this requirement, there is a Private Fix that has been created to ensure these devices are not used when determining a path to failover to. This private fix is available from Symantec Enterprise Technical Support. To obtain the private fix, contact Symantec Support and reference this TechNote during the call. A support representative will be available to assist in troubleshooting this issue.
 
A Private Fix has been created for the following SFW / SFW-HA Products:

SFW 5.1 SP1
SFW 5.1 SP2
SFW 6.0

SFW-HA 5.1 SP1
SFW-HA 5.1 SP2
SFW-HA 6.0

 If it is determined that the private fix addresses the problem, the support representative will further assist in obtaining the private fix. For a complete list of Symantec Enterprise Technical Support contact numbers, go to http://www.symantec.com/enterprise/support/index.jsp

Disclaimer: This fix specifically addresses the problem identified above. It has not been fully tested and should be applied in a test environment before placing into production. If the systems are not critically impaired, it is recommended to delay the installation of this private fix until the next scheduled maintenance release. Before applying this private fix, systems may be required to be upgraded to the latest code base. The support representative will help in determining the best course of action.

Supplemental Materials

SourceEvent ID
Value33
Description

<DSM_name> returned a bogus Path to \Device\MPIODiskX

SourceETrack
Value2774415
Description

During path failure in an Active/Active DMP configuration, 2 luns did not properly move I/O to surviving path and reported 'Bogus Path' errors to the Event Log

Legacy ID



333474


Article URL http://www.symantec.com/docs/TECH75004


Terms of use for this information are found in Legal Notices

Please Sign In

Login using SymAccount.

Knowledge Base Search

Knowledge Base Search

Rate this Article

Help us improve your support experience.

MySymantec

MySymantec

Contacting Support

Contacting Support