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

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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

3. Number of datastores is fairly static

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

Architectural Decision

Enable and Configure Storage I/O control for all datastores.

Set the congestion threshold to 20ms

Leave the shares value default

Add a Step to each SRM recovery Plan as Step 1 and Select the Step Placement of “Before selected step”.

Configure step type as “Command of SRM Server” and execute the Scheduled Task which will disable SIOC prior to executing a SRM recovery

Justification

1. The benefits of Storage I/O control can still be achieved without impact to the SRM solution

2. SIOC will not impact SRM failover as it will be disabled automatically as part of the SRM recovery plan

3. In the event the Protected site or is lost, SIOC will not prevent failover

Implications

1. Increased complexity for the SRM solution

2. An additional step to excecute a “Command of SRM Server” is required

3. A Scheduled Task will need to be setup and configured with setting “Allow task to be ran on demand”

4. A script to disable SIOC will need to be prepared and configured with all datastores

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. Disable Storage I/O control

Relates Articles

1. Example Architectural Decision –  Storage I/O Control for Clusters Protected by SRM (Example 2 – Don’t Use SIOC)

 

Example Architectural Decision – Storage I/O Control for Clusters Protected by SRM (Example 1 – Don’t Use SIOC)

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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)

 

Example Architectural Decision – Storage I/O control for IaaS solutions

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Problem Statement

In vSphere clusters servicing IaaS or Cloud workloads where customers or departments have the ability to self provision virtual machines with varying storage I/O requirements, how can the cluster be configured to ensure the most consistent virtual machine performance from a storage perspective?

Assumptions

1. vSphere 5.1 or later (to support both VMFS and NFS datastores and SIOC Automatic latency threshold computation)

Motivation

1. Ensure consistent storage performance for all virtual machines
2. Prevent a single virtual machine preventing other virtual machines reasonable access to storage

Architectural Decision

Enable Storage I/O control for all datastores and leave the shares values at the default setting for all virtual machines.

Set Tier 1 storage congestion threshold to 10ms – eg: SSD or SAS 15k RPM
Set Tier 2 storage congestion threshold to 20ms – eg: 15k or 10k SAS
Set Tier 3 storage congestion threshold to 30ms – eg: 7.2k SATA

Justification

1. In a IaaS or Cloud environment, it is important to prevent intentional or unintentional DoS type attacks; Storage I/O control will prevent such activities by giving equal access to the storage for all virtual machines attempting concurrent access.
2. Ensure no virtual machine/s monopolize the available I/O of the underlying storage eg: The noisy neighbor issue
3. Storage I/O control ensures consistent access across all ESXi hosts with access to the datastore, not just a single host. This ensures equal I/O access across the environment, not just across a single ESXi host.
4. Tier 1 should maintain lower latency than lower Tier disk, as such, a lower congestion threshold is advisable to ensure optimal performance for virtual machines hosted on Tier 1
5. Virtual machines requiring significant I/O will not be significantly impacted by Storage I/O control (assuming the congestion threshold is reached) as other VMs requiring access to storage will be able to access storage (thanks to Storage I/O control) and complete any required I/O in a timely manner and once the I/O is completed, no longer impact performance at all.
6. Virtual Machine not accessing storage regularly will not impact the VMs accessing storage regularly as Storage I/O control only acts on VMs accessing storage concurrently.
7. Leaving VMs with the default share value decreases administrative overhead and prevents human error granting significantly higher (or lower) share values which may negatively impact performance for one or more VMs

Implications

1. When using Storage DRS with SIOC the Storage DRS I/O latency setting needs to be carefully considered. Setting these value below the SOIC values (assuming Manual latency values are set) is recommended to ensure Storage DRS can work towards evenly balancing the storage workload and improving overall performance & SIOC then can help ensure consistent performance by taking action when the congestion threshold is reached to minimize latency spikes.

Alternatives

1. For vSphere 5.1 environments use the “Automatic Latency Threshold” by selecting the “Percentage of Peak Throughput” and setting the percentage value to “90%”. This setting is designed to minimize the change of a misaligned congestion threshold being manually set, therefore potentially reducing the effectiveness of SIOC
2. Not enable Storage I/O control
3. Enable Storage I/O control and set higher than default share values on critical VMs