VCAP-DCD | Objective 2.5 | Build Performance Requirements into the logical design

Understand what logical performance services are provided by VMware solutions

VMware have a number of performance enhancers in the vSphere, some of which are available in all licence versions, some however require a certain licence level to make the features available.

  • Transparent Page Sharing – Shares identical memory pages across multiple VMs. This is enabled by default. Consideration should be given to try and place similar workloads on the same hosts to gain maximum benefit.
  • Memory Ballooning – Controls a balloon driver which is running inside each VM. When the physical host runs out of memory it instructs the driver to inflate by allocating inactive physical pages. The ESXi host can uses these pages to fulfill the demand from other VMs.
  • Memory Compression – Prior to swapping, memory pages out to physical disks. The ESXi server starts to compress pages. Compared to swapping, compression can improve the overall performance in an memory over commitment scenario.
  • Swapping – As the last resort, ESXi will start to swap pages out to physical disk.
  • vStorage APIs for Array Integration (VAAI) –  is a feature introduced in ESXi/ESX 4.1 that provides hardware acceleration functionality. It enables your host to offload specific virtual machine and storage management operations to compliant storage hardware. With the storage hardware assistance, your host performs these operations faster and consumes less CPU, memory, and storage fabric bandwidth.
  • Storage I/O Control (SIOC) – was introduced in vSphere 4.1 and allows for cluster wide control of disk resources. The primary aim is to prevent a single VM on a single ESX host from hogging all the I/O bandwidth to a shared datastore. An example could be a low priority VM which runs a data mining type application impacting the performance of other more important business VMs sharing the same datastore.
  • vSphere Storage API’s – Storage Awareness (VASA) – VASA is a set of APIs that permits storage arrays to integrate with vCenter for management functionality.
  • Network IO Control (NIOC) – When network I/O control is enabled, distributed switch traffic is divided into the following predefined network resource pools: Fault Tolerance traffic, iSCSI traffic, vMotion traffic, management traffic, vSphere Replication (VR) traffic, NFS traffic, and virtual machine traffic.  You can control the bandwidth each network resource pool is given by setting the physical adapter shares and host limit for each network resource pool.

Identify and differentiate infrastructure qualities (Availability, Manageability, Performance, Recoverability, Security)

This has been covered in a previous Objective.

List the key performance indicators for resource utilisation

According to ITIL, a Key Performance Indicator (KPI) is used to assess if a defined service is running according to expectations. The exact definition of the KPIs differs depending on the area. This objective is about server performance which is typically assessed using the following KPIs: Processor, Memory, Disk, and Network.

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