6.5

Table Of Contents
Monitoring vSphere Flash Read Cache
Flash Read Cache™ lets you accelerate virtual machine performance through the use of host resident ash
devices as a cache.
The vSphere Storage documentation discusses vSphere Flash Read Cache in some detail.
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.
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.
You can manage vSphere Flash Read Cache from the vSphere Web Client. You can monitor Flash Read
Cache by using commands in the esxcli storage vflash namespace. The following table lists available
commands. See the vSphere Command-Line Interface Reference or the online help for a list of options to each
command.
Table 41. Commands for Monitoring vSphere Flash Read Cache
Command Description
storage vflash cache get Gets individual vflash cache info.
storage vflash cache list Lists individual vflash caches.
storage vflash cache stats get Gets vflash cache statistics.
storage vflash cache stats reset Resets vflash cache statistics.
storage vflash device list Lists vflash SSD devices.
storage vflash module get Gets vflash module info.
storage vflash module list Lists vflash modules.
storage vflash module stats get Gets vflash module statistics.
Monitoring and Managing Virtual Volumes
The Virtual Volumes functionality changes the storage management paradigm from managing space inside
datastores to managing abstract storage objects handled by storage arrays.
With Virtual Volumes, an individual virtual machine, not the datastore, becomes a unit of storage
management, while storage hardware gains complete control over virtual disk content, layout, and
management. The vSphere Storage documentation discusses Virtual Volumes in some detail and explains
how to manage them by using the vSphere Web Client.
vSphere Command-Line Interface Concepts and Examples
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