Reduced SAN I/O Multipath configuration



Results: Unavailable storage, downtime 

The signature
Production data accessed with no redundant path

The impact
The existence of a single array port mapping and a single path increases the chances that this storage volume may become unavailable. This may result in increased MTBF and frequent downtime issues. Also, any application which utilizes this storage volume may suffer from sub-optimal performance since I/O load balancing is unavailable (single path from host to the storage array).

Technical details
Typically in production environments it is considered a best practice to:
  - Configure multiple LUN maps (array port mapping) for a storage volume
  - Configure multiple paths for a storage volume

In the example above, a database is stored on three storage volumes. Two of these volumes are configured according to these best practices. However, a third volume which was recently added doesn't comply with the best practices and has only a single array port mapping and a single I/O path.

Can it happen to me?
Yes. In production environments urgent requests are not infrequently, such as the need to add more storage space to specific business services. While handling such urgent matters, details such as redundancy in array port mappings and SAN I/O paths may be forgotten. After the change, everything works properly so the error goes unnoticed. The gap will only be discovered when a recovery is required.