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Four crucial stages
Stage 1: Discovery and analysis. During this phase, a comprehensive inventory of all SAN components is required; it's important to determine the relationship between the hosts and their SAN logical units, logical volumes and physical back-end devices. Once the inventory has been established, all of the hardware and software components need to be checked for compatibility.
This process is open to all sorts of opportunities for human error, and automation is an obvious alternative. One of the greatest challenges is collecting and correlating information obtained from multiple sources. Ensuring this data is accurate is important when analyzing the data to determine if any remediation is required for firmware upgrades or software revision levels.
Stage 2: Planning. Now a detailed data migration plan can be formed. The plan should include a list of servers scheduled for migration, a timetable outlining the schedule, a configuration of the targeted storage devices, and a list of the upgrades necessary
| to bring any hardware or software up to acceptable levels. Automation at this stage enables greater flexibility later, and will allow you to add or remove servers at the last minute by requiring only a simple verification step prior to the migration. Don't shortchange this step; you want to be able to monitor your migration against timetables and checklists.
Stage 3: Migration. Data from the old system is mapped to a new system, usually leveraging some type of migration technology. These are products from a storage vendor or a third party, and they can be array-, host- or network-based appliances or intelligent switches. The most important feature of this technology will be the ability to conduct "online" migrations. Optimally, all data migrations would be accomplished while the systems remain available. The migration automation technology should also let you reverse the migrations process in the event of a software or infrastructure failure. After the migration has been completed, server and hosts need to be remapped to the new volumes, and servers need to be rebooted so applications know where the data now resides. Automating the scripts required to establish these new paths greatly accelerates the time to switch over and eliminates human error.
This was first published in September 2008