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Table Of Contents
Table 151. Using Flash Devices with ESXi
Functionality Description
vSAN vSAN requires flash devices. For more information, see the Administering VMware vSAN
documentation.
VMFS Datastores You can create VMFS datastores on flash devices. Use the datastores for the following
purposes:
n
Store virtual machines. Certain guest operating systems can identify virtual disks
stored on these datastores as flash virtual disks. See Identifying Flash Virtual Disks.
n
Allocate datastore space for the ESXi host swap cache. See Configuring Host Swap
Cache
Virtual Flash Resource (VFFS) Set up a virtual flash resource and use it for the following functionalities:
n
Use as Virtual Flash Read Cache for your virtual machines. See Chapter 16 About
VMware vSphere Flash Read Cache.
n
Allocate the virtual flash resource for the ESXi host swap cache. This method is an
alternative way of host cache configuration that uses VFFS volumes instead of VMFS
datastores. See Configure Host Swap Cache with Virtual Flash Resource.
n
If required by your vendor, use the virtual flash resource for I/O caching filters. See
Chapter 23 Filtering Virtual Machine I/O.
Identifying Flash Virtual Disks
Guest operating systems can identify virtual disks that reside on flash-based datastores as flash virtual
disks.
To verify if this feature is enabled, guest operating systems can use standard inquiry commands such as
SCSI VPD Page (B1h) for SCSI devices and ATA IDENTIFY DEVICE (Word 217) for IDE devices.
For linked clones, native snapshots, and delta-disks, the inquiry commands report the virtual flash status
of the base disk.
Operating systems can detect that a virtual disk is a flash disk under the following conditions:
n
Detection of flash virtual disks is supported on ESXi 5.x and later hosts and virtual hardware version 8
or later.
n
Detection of flash virtual disks is supported only on VMFS5 or later.
n
If virtual disks are located on shared VMFS datastores with flash device extents, the device must be
marked as flash on all hosts.
n
For a virtual disk to be identified as virtual flash, all underlying physical extents should be flash-
backed.
Marking Storage Devices
You can mark storage devices, which are not properly detected, as local flash devices.
When you configure vSAN or set up a virtual flash resource, your storage environment must include local
flash devices.
vSphere Storage
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