LUN migration

LUN migration is a feature of EMC that dynamically migrates data to another LUN or MetaLUN without disrupting running applications. LUN migration has many uses, for example: To select a RAID type that better matches the current performance or availability requirements. To change the type of disk drive (for example, from economical SATA to faster FC, or vice versa). To redesign a LUN with more disk space (expanding the LUN size). After migration is complete, the destination LUN assumes the identity (World Wide Name and other IDs) of the source LUN, and the source LUN is destroyed. LUN migration can be tuned by setting it to one of four speed settings: Low, Medium, High, or ASAP.


Thin LUNs Versus Traditional LUNs

Thin LUNs can be the target or source of LUN migration operations. LUNs can be moved between or within storage pools and or RAID groups. Thin LUNs can be moved to a different storage pool that offers different characteristics to rebalance array performance, or to take advantage of newly available capacity.  For example, thin LUNs can be migrated to a traditional fully allocated LUN if an application in R&D is deployed to production. Traditional LUNs can be migrated to a thin LUN structure if necessary but the physical storage space will remain fully allocated.


As the SAN Storage administrator, the most important is to understand your application requirements and select the approach that meets your needs. If conditions change, you have the option of using LUN migration to migrate from thin LUN to traditional LUN or vice versa.  


Use RAID groups and traditional LUNs:

  • For the best and most predictable performance.
  • When microseconds of performance matters!
  • For precise data placement.
  • When you are not as concerned about space efficiency.
  • When you want one method for all applications and services.


Use thin provisioning with thin pools for:

  • The best space efficiency.
  • Minimal host impact.
  • Easy setup and management.
  • Applications where space consumption is difficult to forecast.
  • Energy and capital savings.


Note: Thin pools and thin LUNs offer many benefits, but it is important to remember that they require careful monitoring and are not suited to every application.