Dell EMC VMAX, Configuration And Best Practices Technical Notes

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During NDM, after
‘symdm create’ cli command is issued and new paths have been discovered by the host, all new native devices on
the target side will have reserve_policy set to single_path. This is PowerPath's default setting for the VMAX array.
According to IBM documentation:
Single_path_reserve: Applies a SCSI2 reserve methodology for the device, which means the device can be accessed only by the
initiator that issued the reserve. This policy prevents other initiators in the same host or on other hosts from accessing the device. That
means only one host can access and use the new disks.
If the NDM Cutover and Commit is issued with the reserve_policy set to single_path for all new native devices, the cluster will not
function correctly since multiple hosts in the cluster need to share the same disks. With the single_path setting, only one host will be
allowed to access the disks.
Therefore it’s important to run the below steps when migrating such environment.
Note: If the customer is able to upgrade PowerPath to 6.1 or is running PowerPath 6.1, then this procedure is not necessary as
PowerPath 6.1 will maintain a no_reserve policy on all new paths.
1. Select Storage Group to migrate.
2. Create the migration session.
3. Discover paths to the host.
3a. Set reserve_policy to no_reserve for all new native devices by running
emc_pp_configure.sh script . This script will configure the
new native devices on the target side into PowerPath by copying the attributes of the PowerPath hdiskpower pseudo devices into the
new native devices and reconfigure the native devices.
4. Cutover Storage Group to VMAX3 or VMAX All Flash array.
5. Monitor for synchronization to complete.
6. Commit the migration.
Note: This script MUST be used in order to perform a migration non-disruptively in this environment. Failing to run the
script following the configuration of the new native target devices can lead to data unavailability.
#! /bin/ksh
devlist=`powermt config 2>&1 | grep -p 0514-034 | grep hdiskpower | awk '{print $5}'`
for pseudo in $devlist
do
pseudo_policy=`lsattr -El $pseudo -a reserve_policy | awk '{print $2}'`
pseudo_prkey=`lsattr -El $pseudo -a PR_key_value | awk '{print $2}'`
nativelist=`powermt display dev=$pseudo | grep -i hdisk| grep -v power | awk '{print $3}'`
echo $nativelist
for native in $nativelist
do
native_policy=`lsattr -El $native -a reserve_policy | awk '{print $2}'`
native_prkey=`lsattr -El $native -a PR_key_value | awk '{print $2}'`
#change reserve_policy and PR_key_value of native(s), whose policy or PR_key_value
#vary from that of pseudo.
if [[ $native_policy != $pseudo_policy || $native_prkey != pseudo_prkey ]]
then
powermt remove dev=$native
echo changing reserve_policy,PR_key_value of $native to $pseudo_policy and $pseudo_prkey
chdev -l $native -a reserve_policy=$pseudo_policy -a PR_key_value=$pseudo_prkey
fi
done
done
powermt config
The script can be downloaded on EMC’s support site:
emc_pp_configure.sh