How to add and remove physical LUNs connected to a server: LINUX dmpdr -o refresh

Description

When adding and removing physical LUNs that are connected to a server, it is necessary to run many steps. To reduce the complexity surrounding the multi-step Dynamic LUN reconfiguration process, Veritas has created a new non-interactive interface to aid the provisioning and removal of devices.

The sequence related to the removal and addition of LUNs is illustrated below:


Figure 1.0

# /usr/lib/vxvm/voladm.d/bin/dmpdr -o refresh

The new enhanced dmpdr tool will only work in connection with Veritas DMP (Dynamic Multi-Pathing). Third-party multi-pathing drivers ( such as MPxIO and EMC PowerPath ) are not supported and will not work with the new interface.

When intentionally removing a LUN from a server, VxVM must be informed prior to any storage activity.

# vxdisk rm <disk-access-name>

The above command informs VxVM that the Veritas disk access (da) name is to be removed from the system. Adding and removing devices must be done at different times and not under the same reconfiguration event. Prior to adding new storage devices, "pre-checks" must be performed to minimize human error.

 

Dmpdr Tool

The enhanced dmpdr tool attempts to make life easier for system and storage administrators, as they no longer require skills in multiple areas.

• The enhanced DMPDR (Dynamic Reconfiguration) tool has been enhanced and now includes a non-interactive interface to aid the complex LUN reconfiguration process
• The DMPDR tool attempts to automate and perform the correct sequence of events on the host in the effort to reduce human error without the need for manual intervention
• The DMPDR tool will try to auto-correct mistakes and refresh the different components in the I/O stack
• The DMPDR tool will clean-up the OS device handles beneath the underlying DMP managed device and refresh VxVM and DMP

LUN Reconfiguration Process

LUN Removal

Figure 2.0

The original LUN removal multi-step process has been replaced with 3 steps:

1. vxdisk rm <Veritas-disk-access-name>
2. Storage Array LUN removal commands and activity
3. /usr/lib/vxvm/voladm.d/bin/dmpdr -o refresh
 

The Peripheral Qualifier/Device Type (PQ) attribute will report a non-zero value when the LUN has been intentionally removed at the Storage Layer:

Example
 

# /etc/vx/diag.d/vxscsiinq -d /dev/vx/dmp/emc0_00aa | head -3

Inquiry for /dev/vx/dmp/emc0_00aa, evpd 0x0, page code 0x0
Peripheral Qualifier/Device Type : 3f

The DMPDR tool will delete stale OS device handles that report a non-zero PQ value automatically.
 

LUN Addition

The OS will NOT automatically detect the presentation of LUNs done at the Storage Array Level.

A manual probe (rescan) of the devices will be required to detect newly provisioned LUNs, the dmpdr tool automates this requirement.

How to manually detect new LUNs:

Example:

#! /bin/ksh

for i in `ls -Ud /sys/class/scsi_host/host*`
do
echo '- - -' > $i/scan
done

The original LUN addition multi-step process has been replaced with 2 steps:

1. Storage Array LUN removal commands/activity
2. /usr/lib/vxvm/voladm.d/bin/dmpdr -o refresh


Note: The dmpdr script will create a log file under /var/adm/vx/ for each LUN reconfiguration event.

The enhanced dmpdr tool functionality is generally available with Veritas Volume Manager Public Patch with 6.1.1 latest patches upwards. Further product enhancements have been made available with InfoScale 7.3.1.x and 7.4.1.x.

Where possible upgrade to the latest InfoScale release.

The dmpdr tool is only available on Solaris and Linux.