6.0.1

Table Of Contents
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To use the flash disk as a virtual flash resource, do not claim this disk for Virtual SAN. If the disk is
claimed by Virtual SAN, remove the disk from Virtual SAN. The flash disk is released from Virtual
SAN and becomes available on the list of disks to use with virtual flash. For information about
removing disks from Virtual SAN, see the Administering VMware Virtual SAN documentation.
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If you intend to use the flash disk with Virtual SAN, do not use the disk for a virtual flash resource. If
the flash disk is used as the virtual flash resource, remove the virtual flash configuration. The disk
becomes available for Virtual SAN. See the vSphere Storage documentation.
Another reason that makes flash disk unavailable is when ESXi cannot detect the disk. See “Local Flash
Disks Are Undetectable,” on page 71.
Keeping Flash Disks VMFS-Free with Auto-Partitioning
When you use auto-partitioning boot option when installing or auto-deploying ESXi, the auto-partitioning
option creates a VMFS datastore on your host's local storage. You have several options to keep your local
storage flash disks unformatted.
Problem
By default, auto-partitioning deploys VMFS file systems on any unused local storage disks on your host,
including flash disks.
However, a flash disk formatted with VMFS becomes unavailable for such features as virtual flash and
Virtual SAN. Both features require an unformatted flash disk and neither can share the disk with any other
file system.
Solution
To ensure that auto-partitioning does not format the flash disk with VMFS, use the following boot options
when you install ESXi or boot the ESXi host for the first time:
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autoPartition=TRUE
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skipPartitioningSsds=TRUE
If you use Auto Deploy, set these parameters on a reference host.
1 In the vSphere Web Client, select the host to use as a reference host and click Manage.
2 Click Settings.
3 Click System to open the system options, and click Advanced System Settings.
4 Scroll to VMkernel.Boot.autoPartition and set the value to true.
5 Scroll to VMkernel.Boot.skipPartitioningSsds and set the value to true.
6 Reboot the host.
If flash disks that you plan to use with Flash Read Cache and Virtual SAN already have VMFS datastores,
remove the datastores.
Local Flash Disks Are Undetectable
If you query for local flash disks during creation of a virtual flash resource or Virtual SAN configuration, the
ESXi host might not return a complete list of the local flash disks.
Problem
ESXi might not be able to automatically detect flash disks, or recognize them as local.
Chapter 7 Troubleshooting Storage
VMware, Inc. 71