Problem Statement

In an environment with one or more clusters with virtual machines protected by SRM, What is the most appropriate configuration of Storage I/O control?

Requirements

1. SRM solution must not be impacted

Assumptions

1. vSphere Version 4.1 or later

2. FC (Block) Based Storage OR NFS (File) based Storage

Constraints

1. Storage I/O control can prevent unmounting of datastore during a Recovery which can lead to errors being reported by SRM

Motivation

1. Where possible ensure consistent storage performance for all virtual machines

2. Simplicity

Architectural Decision

Do not use Storage I/O control for datastores protected by SRM

Justification

1. Storage I/O control can prevent unmounting of datastore during a Recovery which can lead to errors being reported by SRM

2. Storage I/O control can prevent re-mounting of datastore/s during a failback which can lead to errors being reported by SRM and prevent failback without manual intervention

3. Solution does not require any custom steps added to SRM to facilitate a successful recovery

Implications

1. Storage I/O control cannot be used for Datastores protected by SRM

2. In the event of storage contention, SIOC will not be able to ensure fairness between virtual machines based on their share values

3. Storage Performance may degrade significantly during contention

Alternatives

1. Enable Storage I/O control and leave default settings

2. Enable storage I/O control and set share values on virtual machines

3. Enable Storage I/O control and set a lower “congestion threshold”

4. Enable Storage I/O control and set a higher “congestion threshold”

5. Enable Storage I/O control and as part of the DR runsheet, disable SIOC prior to executing a SRM recovery

Relates Articles

1. Example Architectural Decision –  Storage I/O Control for Clusters Protected by SRM (Example 2 – Use SIOC)