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Table Of Contents
Managing Storage I/O
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vSphere Storage I/O Control allows cluster-wide storage I/O prioritization, which allows better workload
consolidation and helps reduce extra costs associated with over provisioning.
Storage I/O Control extends the constructs of shares and limits to handle storage I/O resources. You can
control the amount of storage I/O that is allocated to virtual machines during periods of I/O congestion,
which ensures that more important virtual machines get preference over less important virtual machines
for I/O resource allocation.
When you enable Storage I/O Control on a datastore, ESXi begins to monitor the device latency that
hosts observe when communicating with that datastore. When device latency exceeds a threshold, the
datastore is considered to be congested and each virtual machine that accesses that datastore is
allocated I/O resources in proportion to their shares. You set shares per virtual machine. You can adjust
the number for each based on need.
The I/O filter framework (VAIO) allows VMware and its partners to develop filters that intercept I/O for
each VMDK and provides the desired functionality at the VMDK granularity. VAIO works along Storage
Policy-Based Management (SPBM) which allows you to set the filter preferences through a storage policy
that is attached to VMDKs.
Configuring Storage I/O Control 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.
By default, all virtual machine shares are set to Normal (1000) with unlimited IOPS.
Note Storage I/O Control is enabled by default on Storage DRS-enabled datastore clusters.
Note In this chapter, "Memory" refers to physical RAM.
This chapter includes the following topics:
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About Virtual Machine Storage Policies
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About I/O Filters
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Storage I/O Control Requirements
VMware, Inc.
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