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August 08, 2013

Is there a benefit using vSphere’s Storage Control with Atlantis ILIO?

Andrew Wood - Atlantis


Had an interesting question from a customer today where they asked – is it recommended to enable Storage I/O control for an Atlantis ILIO NFS datastore?



What is Storage I/O Control for?

As Alantis Computing’s Jim Moyle discussed at Briforums in London and Chicago “Storage Improvements in vSphere 5.0” Storage I/O Control (SIOC) was introduced in vSphere 4.1. It was introduced to provide I/O prioritization of virtual machines running on a cluster of ESX servers that had access to a shared, iSCSI or FC, storage pool. It extended the familiar constructs of shares and limits, which existed for CPU and memory, to address storage utilization through a dynamic allocation of I/O queue slots across a cluster of ESX servers.


Objective for SOIC

vSphere 5.0 extends Storage I/O Control (SIOC) to provide cluster-wide I/O shares and limits for NFS datastores. This means that no single virtual machine should be able to create a bottleneck in any environment regardless of the type of shared storage used. SIOC automatically throttles a virtual machine which is consuming a disparate amount of I/O bandwidth when the configured latency threshold has been exceeded, in this example that is the data mining virtual machine which happens to reside on a different host. To allow for other virtual machines receiving their fair share of I/O bandwidth using the same datastore a share based fairness mechanism has been created which now is supported on both NFS and VMFS.

Storage I/O Control (SIOC) is used to control the I/O usage of virtual machines to gradually enforce the predefined I/O share levels. It is designed for server workloads (rather than for VDI) on traditional SAN arrays where you may have servers that are making heavy storage I/O demand and you want to limit that demand. For more information check the VMware Technical Resources on storage IO control.

If you were to configuring Storage I/O Control, it is a two-step process:

1 Enable Storage I/O Control for the datastore

2 Set the number of storage I/O shares and upper limit of I/O operations per second (IOPS) allowed for each virtual machine.

You can review this in more depth in the vSphere Resource Management Guide

Note  by default, all virtual machine shares are set to Normal (1000) with unlimited IOPS.


Is it recommended to enable Storage IO Control with an Atlantis ILIO NFS Datastore?

In short – no.

In long – for an Atlantis ILIO NFS datastore we don’t need to limit the amount of IOPS available. The goal of Atlantis ILIO is to optimise the storage performance and provide abundant IOPS at low latency in order to give great performance for your virtual desktop and shared hosted desktop workloads. We want to give as much performance as possible: as such there would be no reason to enable SIOC on the datastore, because you wouldn’t want to limit the IOPS of a particular VM hosted on it.

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