Veritas DMP VMware environments not showing DMP extended attributes for srdf-r1 and srdf-r2 as scsix:y.ignoreDeviceInquiryCache is not set to true

Problem

In VMware environments, Veritas DMP Multi-pathing may not report the correct Veritas DMP extended attributes due to failed SCSI inquiry requests.

Additionally, even after the LUN has been made Read/Write (RW), it still show up as Write Disabled (WD) under the scsi inquiry.

Certain guest operating systems or applications that run inside a Virtual Machine can display unpredictable behaviour.

Error Message

Veritas Volume Manager (VxVM) is failing to report consistent DMP extended attribute information for the following EMC "srdf-r2" LUNs:

# vxdisk -eo alldgs list
DEVICE       TYPE           DISK        GROUP        STATUS               OS_NATIVE_NAME   ATTR
emc0_042e    auto:none      -            -           online invalid thinrclm sdc              WD srdf-r2 tprclm
emc0_042f    auto:none      -            -           online invalid thinrclm sdd              tprclm
emc0_0430    auto:none      -            -           online invalid thinrclm sde              tprclm
emc0_0431    auto:none      -            -           online invalid thinrclm sdf              tprclm
sda          auto:LVM       -            -           LVM                  sda              -
sdb          auto:LVM       -            -           LVM                  sdb              -

Cause

Certain Virtual Machines (VM) must obtain the SCSI INQUIRY information from the LUN instead of using SCSI INQUIRY data cached by ESXi.

This can happen due to the way RDM works on ESX. RDM will actually cache SCSI inquiry data and may fail to pickup changes.

Essentially, the SCSI inquiry data Veritas obtains from the ESX host can be out of date (stale), and does not reflect the current LUN attributes or the revised status of the LUN.

When the ESXi host first connects to a target storage device, it issues the SCSI INQUIRY command to obtain basic identification data from the device. By default, ESXi caches the received SCSI INQUIRY data (Standard, page 80, and page 83), and the data remains unchanged afterwards. Responses for subsequent SCSI INQUIRY commands are returned from the cache.

However, specific guest operating systems running in virtual machines with RDMs must query the LUN instead of using SCSI INQUIRY data cached by ESXi. In these cases, you can configure the VM to ignore the SCSI INQUIRY cache.

Solution

VMware related

The VMware administrators will need to set scsix:y.ignoreDeviceInquiryCache = "true" on all VM machines.

Once set, power off and on for the VMware setting to take effect.

Steps:

Modify the .vmx file of the virtual machine with the RDM

Use this method for VMs with hardware version 8 or later.

1.] Add the following parameters to the file:

scsix:y.ignoreDeviceInquiryCache = "true"

NOTE: Where x is the SCSI controller number and y is the SCSI target number of the RDM.

2.] Reboot the VM.

Or this can be done from the UI, for example below.

a. Connect to the ESXi server

b. Click Edit Settings, then select “VM Options”.

c. Scroll down to “Configuration Parameters” and click “Edit Configuration”.

d. Click “Add parameter”.

e. For each RDM LUN add ‘ignoreDeviceInquiryCache’ as below.

Key = scsiX:Y.ignoreDeviceInquiryCache

Value = true

where X and Y are the SCSI controller number and SCSI target number.

Example:

Click OK and Save settings.

Reboot the VM.

Revised VxVM output:

# vxdisk -eo alldgs list
DEVICE       TYPE           DISK        GROUP        STATUS               OS_NATIVE_NAME   ATTR
emc0_042e    auto:none      -            (srdfdg)     online thinrclm     sdc              WD srdf-r2 tprclm
emc0_042f    auto:none      -            (srdfdg)     online thinrclm     sdd              WD srdf-r2 tprclm
emc0_0430    auto:none      -            (srdfdg)     online thinrclm     sde              WD srdf-r2 tprclm
emc0_0431    auto:none      -            (srdfdg)     online thinrclm     sdf              WD srdf-r2 tprclm
sda          auto:LVM       -            -           LVM                  sda              -
sdb          auto:LVM       -            -           LVM                  sdb              -

NOTE: Veritas DMP is now able to see the DMP extended attributes for the above EMC sdrf-r2 devices.