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Table Of Contents
Storage I/O Control Requirements
Storage I/O Control has several requirements and limitations.
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Datastores that are Storage I/O Control-enabled must be managed by a single vCenter Server
system.
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Storage I/O Control is supported on Fibre Channel-connected, iSCSI-connected, and NFS-connected
storage. Raw Device Mapping (RDM) is not supported.
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Storage I/O Control does not support datastores with multiple extents.
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Before using Storage I/O Control on datastores that are backed by arrays with automated storage
tiering capabilities, check the VMware Storage/SAN Compatibility Guide to verify whether your
automated tiered storage array has been certified to be compatible with Storage I/O Control.
Automated storage tiering is the ability of an array (or group of arrays) to migrate LUNs/volumes or
parts of LUNs/volumes to different types of storage media (SSD, FC, SAS, SATA) based on user-set
policies and current I/O patterns. No special certification is required for arrays that do not have these
automatic migration/tiering features, including those that provide the ability to manually migrate data
between different types of storage media.
Storage I/O Control Resource Shares and Limits
You allocate the number of storage I/O shares and upper limit of I/O operations per second (IOPS)
allowed for each virtual machine. When storage I/O congestion is detected for a datastore, the I/O
workloads of the virtual machines accessing that datastore are adjusted according to the proportion of
virtual machine shares each virtual machine has.
Storage I/O shares are similar to shares used for memory and CPU resource allocation, which are
described in Resource Allocation Shares. These shares represent the relative importance of a virtual
machine regarding the distribution of storage I/O resources. Under resource contention, virtual machines
with higher share values have greater access to the storage array. When you allocate storage I/O
resources, you can limit the IOPS allowed for a virtual machine. By default, IOPS are unlimited.
The benefits and drawbacks of setting resource limits are described in Resource Allocation Limit. If the
limit you want to set for a virtual machine is in terms of MB per second instead of IOPS, you can convert
MB per second into IOPS based on the typical I/O size for that virtual machine. For example, to restrict a
back up application with 64 KB IOs to 10 MB per second, set a limit of 160 IOPS.
View Storage I/O Control Shares and Limits
You can view the shares and limits for all virtual machines running on a datastore. Viewing this
information allows you to compare the settings of all virtual machines that are accessing the datastore,
regardless of the cluster in which they are running.
Procedure
1 Browse to the datastore in the vSphere Client.
vSphere Resource Management
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