6.0.1

Table Of Contents
About VMware vSphere Flash Read
Cache 15
Flash Read Cache™ lets you accelerate virtual machine performance through the use of host resident ash
devices as a cache.
You can reserve a Flash Read Cache for any individual virtual disk. The Flash Read Cache is created only
when a virtual machine is powered on, and it is discarded when a virtual machine is suspended or powered
o. When you migrate a virtual machine you have the option to migrate the cache. By default the cache is
migrated if the virtual ash module on the source and destination hosts are compatible. If you do not
migrate the cache, the cache is rewarmed on the destination host. You can change the size of the cache while
a virtual machine is powered on. In this instance, the existing cache is discarded and a new write-through
cache is created, which results in a cache warm up period. The advantage of creating a new cache is that the
cache size can beer match the application's active data.
Flash Read Cache supports write-through or read caching. Write-back or write caching are not supported.
Data reads are satised from the cache, if present. Data writes are dispatched to the backing storage, such as
a SAN or NAS. All data that is read from or wrien to the backing storage is unconditionally stored in the
cache.
Flash Read Cache does not support RDMs in physical compatibility. Virtual compatibility RDMs are
supported with Flash Read Cache.
Watch the video for more information about Flash Read Cache.
Conguring vSphere Flash Read Cache
(hp://link.brightcove.com/services/player/bcpid2296383276001?
bctid=ref:video_cong_vsphere_ash_read_cache)
N Not all workloads benet with a Flash Read Cache. The performance boost depends on your
workload paern and working set size. Read-intensive workloads with working sets that t into the cache
can benet from a Flash Read Cache conguration. By conguring Flash Read Cache for your read-intensive
workloads additional I/O resources become available on your shared storage, which can result in a
performance increase for other workloads even though they are not congured to use Flash Read Cache.
This chapter includes the following topics:
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“DRS Support for Flash Read Cache,” on page 142
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“vSphere High Availability Support for Flash Read Cache,” on page 142
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“Congure Flash Read Cache for a Virtual Machine,” on page 142
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“Migrate Virtual Machines with Flash Read Cache,” on page 143
VMware, Inc.
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