Transparent Page Sharing (TPS) Example Architectural Decisions Register

The following is a register of all Example Architectural Decisions related to Transparent Page Sharing on VMware ESXi following the announcement from VMware that TPS will be disabled by default in future patches and versions.

See The Impact of Transparent Page Sharing (TPS) being disabled by default for more information.

The goal of this series is to give the pros and cons for multiple options for the configuration of TPS for a wide range of virtual workloads from VDI, to Server, Business Critical Apps , Test/Dev and QA/Pre-Production.

Business Critical Applications (vBCA) :

1. Transparent Page Sharing (TPS) Configuration for Virtualized Business Critical Applications (vBCA)

Mixed Server Workloads:

1. Transparent Page Sharing (TPS) Configuration for Production Servers (1 of 2)

2. Transparent Page Sharing (TPS) Configuration for Production Servers (2 of 2) – Coming Soon!

Virtual Desktop (VDI) Environments:

1. Transparent Page Sharing (TPS) Configuration for VDI (1 of 2)

2. Transparent Page Sharing (TPS) Configuration for VDI (2 of 2)

Testing & Development:

1. Transparent Page Sharing (TPS) Configuration for Test/Dev Servers (1 of 2) – Coming Soon!

2. Transparent Page Sharing (TPS) Configuration for Test/Dev Servers (2 of 2) – Coming Soon!

QA / Pre-Production:

1. Transparent Page Sharing (TPS) Configuration for QA / Pre-Production Servers

Related Articles:

1. Example Architectural Decision Register

2. The Impact of Transparent Page Sharing (TPS) being disabled by default – @josh_odgers (VCDX#90)

3. Future direction of disabling TPS by default and its impact on capacity planning – @FrankDenneman (VCDX #29)

4. Transparent Page Sharing Vulnerable, Yet Largely Irrelevant – @ChrisWahl (VCDX#104)

Example Architectural Decision – Transparent Page Sharing (TPS) Configuration for Mixed Production Servers (1 of 2)

Problem Statement

In a VMware vSphere environment, with future releases of ESXi disabling Transparent Page Sharing by default, what is the most suitable TPS configuration for an environment running mixed production server workloads?

Assumptions

1. TPS is disabled by default
2. Storage is expensive
3. Two Socket ESXi Hosts have been chosen to align with a scale out methodology.
4. Average Server VM is between 2-4vCPU and 4-8GB Ram with some larger.
5. Memory is the first compute level constraint.
6. HA Admission Control policy used is “Percentage of Cluster Resources reserved for HA”
7. vSphere 5.5 or earlier

Requirements

1. The environment must deliver consistent performance
2. Minimize the cost of shared storage

Motivation

1. Reduce complexity where possible.
2. Maximize the efficiency of the infrastructure

Architectural Decision

Leave TPS disabled (default) and leave Large Memory pages enabled (default).

Justification

1. Setting 100% memory reservations ensures consistent performance by eliminating the possibility of swapping.
2. The 100% memory reservation also eliminates the capacity usage by the vswap file which saves space on the shared storage as well as reducing the impact on the storage in the event of swapping.
3. RAM is cheaper than Tier 1 storage (which is recommended for vSwap storage to ensure minimal performance impact during swapping) so the increased cost of memory in the hosts is easily offset by the saving in Tier 1 shared storage.
4. Simplicity. Leaving default settings is advantageous from both an architectural and operational perspective.  Example: ESXi Patching can cause settings to revert to default which could negate TPS savings and put a sudden high demand on storage where TPS savings are expected.
5. TPS savings for server workloads is typically much less than with desktop workloads and as a result less attractive.
6. The decision has been made to use 2 socket ESXi hosts and scale out so the TPS savings per host compared to a 4 socket server with double the RAM will be lower.
7. HA admission control will calculate fail-over requirements (when using Percentage of cluster resources reserved for HA) so that performance will be approximately the same in the event of a fail-over due to reserving the full RAM reserved for every VM leading to more consistent performance under a wider range of circumstances.
8. Lower core count (and lower cost) CPUs will likely be viable as RAM will likely be the first constraint for further consolidation.
9. Remove the real or perceived security risk of sensitive information being gathered from other VMs using TPS as described in VMware KB 2080735

Implications

1. Using 100% memory reservations requires ESXi hosts and the cluster be sized at a 1:1 ratio of vRAM to pRAM (Physical RAM) and should include N+1 so a host failure can be tolerated.
2. Increased RAM costs
3. No memory overcommitment can be achieved
4. Potential for lower CPU utilization / overcommitment as RAM may become the first constraint.

Alternatives

1. Use 50% reservation and enable TPS
2. Use no reservation, Enable TPS and disable large pages

Related Articles:

1. The Impact of Transparent Page Sharing (TPS) being disabled by default @josh_odgers (VCDX#90)

2. Example Architectural Decision – Transparent Page Sharing (TPS) Configuration for Production Servers (2 of 2)

3. Future direction of disabling TPS by default and its impact on capacity planning –@FrankDenneman (VCDX #29)

4. Transparent Page Sharing Vulnerable, Yet Largely Irrelevant – @ChrisWahl (VCDX#104)