What is VMware Storage Masking and what are the best practices around Storage Masking? Duncan Epping tackles both these questions in a recent article on yellow-bricks.com. VMware has a best practice pertaining to masking LUNs on a per cluster basis. The best practice has been around for years and basically is there to reduce conflicts. More hosts accessing the same LUNs means more overhead, just to give you an example every 5 minutes a rescan of both HBAs takes place automatically to check for dead storage paths. You can imagine that there's a difference between 32+ hosts accessing your storage or limiting it to for instance 16 hosts.
Masking helps performance, but has a potential to lessen flexibility. Duncan explains a way to use a so called "Transfer Volume" to regain the lost flexibility when using masking.
Here's the process:
- Storage VMotion the VM from LUN on Array 1 to Transfer LUN
- VMotion VM from Cluster A to Cluster B
- Storage VMotion the VM from Transfer LUN to LUN on Array 2