Error Message

When one I/O Domain is shutdown and the LDOM Virtual Disk Client (VDC) fails over the I/O to the alternate Virtual Disk Server (VDS), DMP returns I/O error after the failover because of PGR Reservation Conflict.

Mar 30 18:59:11 hostA vdc: [ID 990228 kern.info] vdisk@0 is offline
Mar 30 18:59:12 hostA vdc: [ID 979497 kern.info] vdisk@1 access to service failed using ldc@26,0
Mar 30 18:59:14 hostA vdc: [ID 625787 kern.info] vdisk@2 is online using ldc@35,1

Mar 30 18:59:31 hostA vxdmp: [ID 443116 kern.notice] NOTICE: VxVM vxdmp V-5-0-0 i/o error occured (errno=0x5) on dmpnode 27/0x12

Log messages from the /etc/vx/dmpevents.log:

Fri Mar 30 18:59:30.079: I/O error occured on Path c0d1s2 belonging to Dmpnode c0d1s2
Fri Mar 30 18:59:30.559: I/O analysis done as DMP_PATH_OKAY on Path c0d1s2 belonging to Dmpnode c0d1s2
Fri Mar 30 18:59:30.559: I/O retry(299999999) on Path c0d1s2 belonging to Dmpnode c0d1s2
Fri Mar 30 18:59:31.066: Unmarked as idle Path c0d1s2 belonging to Dmpnode c0d1s2
Fri Mar 30 18:59:31.279: SCSI error occured on Path c0d1s2: opcode=0x2a reported reservation conflict (status=0x18, key=0x0, asc=0x0, ascq=0x0)
Fri Mar 30 18:59:31.279: I/O analysis done as DMP_DISK_FAILURE on Path c0d1s2 belonging to Dmpnode c0d1s2
Fri Mar 30 18:59:31.279: I/O error occured (errno=0x5) on Dmpnode c0d1s2
 

SCSI3 PGR I/O Fencing is only supported with Veritas (VRTS)  Dynamic Multipathing (DMP) and EMC Powerpath.   SCSI3 PGR I/O Fencing is not supported with other Third Party DMP (TPD) solutions with the exception of EMC Powerpath.  When the disk paths are controlled by TPD solutions, VRTS DMP does not have (unable to) control on how the PGR key registration will be handled by TPD.  

In cases where TPD presents multiple logical paths of the same disk to DMP, TPD is at liberty to re-route the PGR key reservation operations to any of the physical paths controlled by the TPD.   If the TPD re-routes some of the key reservation operations to the same physical path, some of the other physical paths will not have the PGR key registered even though DMP has already issued the key reservation operation to those logical paths.

In situations where the TPD presents only one single logical path for each disk (like the LDOM MPGROUP) to DMP, DMP doesn't have control if the TPD registers the key to all the paths that the TPD controls.   If the TPD chooses to register the PGR key on one single physical path, all other physical paths will not have the required key registration.

In both of the above situations, when the TPD fails over the I/O to the alternate physical path, the alternate physical path may not have the PGR key registered and the diskarray will reject the I/O with reservation conflict error.    Like the case in MPGROUP, when the VDC fails over the I/O to the alternate VDS, the physical disk path controlled by the alternate VDS does not have the PGR key registered and the diskarray rejected the I/O with reservation conflict as shown in the /etc/vx/dmpevents.log.

Fri Mar 30 18:59:31.279: SCSI error occured on Path c0d1s2: opcode=0x2a reported reservation conflict (status=0x18, key=0x0, asc=0x0, ascq=0x0)
 

SCSI3 PGR I/O Fencing is only supported with Veritas DMP.

It is necessary to remove the LDOM MPGROUP configuration and present all the physical paths to the LDOM Guest Domain. Enabling Veritas DMP running in the Guest Domain to control the physical paths and provide the multipathing is the recommended/supported configuration.

Applies To

Veritas Volume Manager (VxVM) running in LDOM Guest Domain with LDOM MPGROUP configured in the LDOM I/O Domains to provide multipathing for the disks.