HP 3PAR Online Import for EMC Storage Data Migration Guide

Planning for Migration
Advanced planning ensures that you achieve the desired results when migrating data.
• It is a recommended best practice to make a backup of your host/data before starting a
migration.
• To perform a minimally disruptive migration process, a maintenance window outage is required.
Please plan accordingly.
• Identify which virtual disks and hosts will be migrated. If you will not be migrating all the
virtual disks presented to a host, you must unpresent the virtual disks that you do not want
migrated. Otherwise, all the virtual disks will be implicitly included in the migration.
• Determine if you will be using thin or full provisioning on the destination storage system. This
decision impacts the amount of capacity needed on the destination storage system.
• Before starting the migration, you should consider creating a snapshot of each virtual disk
that will be migrated.
• Because there is some impact on performance, you may want to schedule migrations during
off-peak hours, if possible.
• To optimize the rate at which data is migrated from the source, hosts with a lighter load/less
data should be migrated first.
• When selecting objects for migration, be aware of any overlap or sharing of virtual disks
between hosts. In this situation, selecting a host or a virtual disk in any set will result in every
virtual disk and every host in all sets being implicitly selected for migration due to the overlap.
For additional information refer to “Supported and Unsupported Migrations by HP 3PAR
Online Import Utility for EMC Storage” (page 17).
Reconfiguring the Host DSM
When migrating a host, a minimally disruptive migration (MDM) process is used. This involves
reconfiguring the host DSM used to communicate with the storage system from an EMC DSM to a
native Multipathing software DSM (For Windows it is MPIO and for Linux it is Device Mapper).
After the migration preparation phase is complete, the host must be shutdown and reconfigured
to use the native Multipathing software DSM.
NOTE: When reconfiguring a host to use the native Microsoft MPIO DSM on Windows 2008
R2 or Windows 2012, use 3PARdataVV as the device hardware ID.
NOTE: When reconfiguring a host, use the native Linux Device Mapper DSM, whitelist the 3PAR
specific information in multipath.conf.
IMPORTANT: In Linux, PowerPath devices are presented as /dev/emcpower* (i.e.
/dev/emcpowea ). PowerPath removal in Linux ALSO removes this device type. This changes when
multipath assumes management of these devices. For example, before PowerPath removal consider
/dev/sdb and /dev/sdc being combined to /dev/emcpowera. After PowerPath removal, /dev/sdb
and /dev/sdc would be represented by /dev/mpathx. This represents a challenge for customers
who use direct device referencing in /etc/fstab or other custom scripts. It is generally advised that
fstab mounts are performed using blkid/uuid, however this is not always employed. Consider
/dev/emcpowera being mounted as /var. After PowerPath removal, /var would not automatically
mount to /dev/mpathx.
The data transfer migration phase is then started, and the host is brought back online. This process
ensures that the host is never multipathing between the source EMC Storage system and the
destination HP 3PAR StoreServ Storage system. Even if the native Multipathing software DSM is
already configured, it is necessary to restart the host after unzoning the source EMC Storage system
from the host.
24 Preparing for Data Migration