Tuesday 15 March 2016

Storage I/O Control

Storage I/O Control Overview

  • SIOC is a method to ensure that the VM's on datastore get a fair share of I/O resources during the period of high contention or latency.
  • Important Virtual Machines get preferences when compared to less important Virtual Machines for I/O resource allocation.
  • Can be used both with and without Storage DRS as it includes two different thresholds i.e Standalone without DRS and with vSphere Storage DRS.
  • SIOC is aware about the average latency, active VM's and also the priorities associated with them.
  • Quite Similar to the concept used by DRS for CPU/Memory the higher the shares value higher the resources it get.
  • vCenter is only used for enabling and disabling the feature and for changing the thresholds.

SIOC Requirements

  • SIOC is supported on FC,ISCSI, and NFS not supported with Raw Device Mapping (RDM)
  • vSphere Enterprise Plus License.
  • Datastore which are SIOC enabled must be managed by single vCenter Server.

How It Works?

  • To configure the vSphere SIOC enable it for the particular datastore as it is disabled by default.
  • Set the number of storage I/O shares for each VM's and limit for IOPS by default the limit is unlimited.
  • Once Enabled ESXi starts monitoring the latency when communicating with the datastore and if it exceeds the threshold value means it's congested
  • SIOC uses Workload Injector Based Model and only runs when the datastore is in an ideal state.
  • It automatically determines the latency, moreover this can also be overridden by specifying specific latency value.
  • Automatic detection works well when you have multiple disk arrays and many datastore are configured for SIOC.

For More information refer vSphere Documentation Center