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Example Architectural Decision – Network I/O Control Shares/Limits for ESXi Host using IP Storage

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Problem Statement

With 10GB connections becoming the norm, ESXi hosts will generally have less physical connections than in the past where 1Gb was generally used, but more bandwidth per connection (and in total) than a host with 1GB NICs.

In this case, the hosts have only to 2 x 10GB NICs and the design needs to cater for all traffic (including IP storage) for the ESXi hosts.

The design needs to ensure all types of traffic have sufficient burst and sustained bandwidth for all traffic types without significantly negatively impacting other types of traffic.

How can this be achieved?

Assumptions

1. No additional Network cards (1gb or 10gb) can be supported
2. vSphere 5.1
3. Multi-NIC vMotion is desired

Constraints

1. Two (2) x 10GB NICs

Motivation

1. Ensure IP Storage (NFS) performance is optimal
2.Ensure vMotion activities (including a host entering maintenance mode) can be performed in a timely manner without impact to IP Storage or Fault Tolerance
3. Fault tolerance is a latency-sensitive traffic flow, so it is recommended to always set the corresponding resource-pool shares to a reasonably high relative value in the case of custom shares.
4. Proactively address potential contention due to limited physical network interfaces

Architectural Decision

Use one dvSwitch to support all VMKernel and virtual machine network traffic.

Enable Network I/O control, and configure NFS and/or iSCSI traffic with a share value of 100 and ESXi Management , vMotion & FT which will have share value of 25. Virtual Machine traffic will have a share value of 50.

Configure the two (2) VMKernel’s for IP Storage on dvSwitch and set to be Active on one 10GB interface and Standby on the second.

Configure two VMKernel interfaces for vMotion on the dvSwitch and set the first as Active on one interface and standby on the second.

A single VMKernel will be configured for Fault tolerance and will be configured as Active on one interface and standby on the second.

For ESXi Management, the VMKernel will be configured as Active on the interface where FT is standby and standby on the second interface.

All dvPortGroups for Virtual machine traffic will be active on both interfaces.

Justification

1. The share values were chosen to ensure IP storage traffic is not impacted as this can cause flow on effects for the environments performance. vMotion & FT are considered important, but during periods of contention, should not monopolize or impact IP storage traffic.
2. IP Storage is more critical to ongoing cluster and VM performance than ESXi Management, vMotion or FT
3. IP storage requires higher priority than vMotion which is more of a burst activity and is not as critical to VM performance
4. With a share value of 25,  Fault Tolerance still has ample bandwidth to support the maximum supported FT machines per host of 4 even during periods of contention
5. With a share value of 25, vMotion still has ample bandwidth to support multiple concurrent vMotion’s during contention however performance should not be impacted on a day to day basis. With up to 8 vMotion’s supported as it is configured on a 10GB interface. (Limit of 4 on a 1GB interface) Where no contention exists, vMotion traffic can burst and use a large percentage of both 10GB interfaces to complete vMotion activity as fast as possible
6. With a share value of 25,  ESXi Management still has ample bandwidth to continue normal operations even during periods of contention
7. When using bandwidth allocation, use “shares” instead of “limits,” as the former has greater flexibility for unused capacity redistribution.
8. With a share value of 50,  Virtual machine traffic still has ample bandwidth and should result in minimal or no impact to VM performance across 10Gb NICs
9. Setting Limits may prevent operations from completing in a timely manner where there is no contention

Implications

1. In the unlikely event of significant and ongoing contention, performance for vMotion may affect the ability to perform the evacuation of a host in a timely manner. This may extend scheduled maintenance windows.
2. VMs protected by FT may be impacted

Alternatives

1. Use a share value  of 50 for IP storage traffic to more evenly share bandwidth during periods of contention. However this may impact VM performance eg: Increased CPU WAIT if the IP storage is not keeping up with the storage demand

Related Posts
1. Example VMware vNetworking Design for IP Storage (4 x 10GB NICs)
2. Example VMware vNetworking Design for IP Storage (2 x 100GB NICs)
3. Frank Denneman (VCDX) – Designing your vMotion Network – Multi-NIC vMotion & NIOC

Example VMware vNetworking Design for IP Storage

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On a regular basis, I am being asked how to configure vNetworking to support environments using IP Storage (NFS / iSCSI).

The short answer is, as always, it depends on your requirements, but the below is an example of a solution I designed in the past.

Requirements

1. Provide high performance and redundant access to the IP Storage (in this case it was NFS)
2. Ensure ESXi hosts could be evacuated in a timely manner for maintenance
3. Prevent significant impact to storage performance by vMotion / Fault Tolerance and Virtual machines traffic
4. Ensure high availability for ESXi Management / VMKernel and Virtual Machine network traffic

Constraints

1. Four (4) x 10GB NICs
2. Six (6) x 1Gb NICs (Two onboard NICs and a quad port NIC)

Note: So in my opinion the above NICs are hardly “constraining” but still important to mention.

Solution

Use a standard vSwitch (vSwitch0) for ESXi Management VMKernel. Configure vmNIC0 (Onboard NIC 1) and vmNIC2 (Quad Port NIC – port 1)

ESXi Management will be Active on vmNIC0 and vmNIC2 although it will only use one path at any given time.

Use a Distributed Virtual Switch (dvSwitch-admin) for IP Storage , vMotion and Fault Tolerance.

Configure vmNIC6 (10Gb Virtual Fabric Adapter NIC 1 Port 1) and vmNIC9 (10Gb Virtual Fabric Adapter NIC 2 Port 2)

Configure Network I/O with NFS traffic having a share value of 100 and vMotion & FT will each have share value of 25

Each VMKernel for NFS will be active on one NIC and standby on the other.

vMotion will be Active on vmNIC6 and Standby on vmNIC9 and Fault Tolerance vice versa.

vNetworking Example dvSwitch-Admin

Use a Distributed Virtual Switch (dvSwitch-data) for Virtual Machine traffic

Configure vmNIC7 (10Gb Virtual Fabric Adapter NIC 1 Port 2) and vmNIC8 (10Gb Virtual Fabric Adapter NIC 2 Port 1)

Conclusion

While there are many ways to configure vNetworking, and there may be more efficient ways to achieve the requirements set out in this example, I believe the above configuration achieves all the customer requirements.

For example, it provides high performance and redundant access to the IP Storage by using two (2)  VMKernel’s each active on one 10Gb NIC.

IP storage will not be significantly impacted during periods of contention as Network I/O control will ensure in the event of contention that the IP Storage traffic has ~66% of the available bandwidth.

ESXi hosts will be able to be evacuated in a timely manner for maintenance as

1. vMotion is active on a 10Gb NIC, thus supporting the maximum 8 concurrent vMotion’s
2. In the event of contention, worst case scenario vMotion will receive just short of 2GB of bandwidth. (~1750Mb/sec)

High availability is ensured as each vSwitch and dvSwitch has two (2) connections from physically different NICs and connect to physically separate switches.

Hopefully you have found this example helpful and for a example Architectural Decision see Example Architectural Decision – Network I/O Control for ESXi Host using IP Storage