vsphere-esxi-vcenter-server-55-storage-guide

Chapter 21 About VMware vSphere Flash Read CacheMigrating Virtual Machines with Flash Read CacheYou can migrate virtual machines with Flash Read Cache.Procedure1 Right-click the virtual machine and select Migrate2 Select Change Host.3 Select the destination host.4 Under Select Flash Read Cache Settings, select Always Migrate Flash Read Cache.Flash Read CacheMigration SettingsAutomaticMigrateDiscardDescriptionMigrate the Flash Read Cache if possible.Migration will proceed only if the Flash Read Cache can be migrated to the targetdestination. This option is useful when the cache is small or the cache size closely matchesthe application's active data.Flash Read Cache is not migrated, the cache is dropped. This option is useful when thecache size is large or the cache size is larger than the application's active data.5 Click Finish.Local SSDs Are Unavailable for Use with Virtual FlashWhen a local SSD disk is used for Virtual SAN or is formatted as VMFS, it becomes unavailable for virtualflash.ProblemA local SSD disk does not appear on the list of disks to be used by virtual flash.CauseThis problem occurs when you format a local SSD disk as VMFS or use the disk for Virtual SAN. Virtualflash and Virtual SAN are mutually exclusive consumers of SSD disks and configure SSDs differently.Virtual flash and Virtual SAN cannot share the same SSD disk. Virtual flash cannot share the SSD disk withother file systems including VMFS.SolutionUse only unformatted SSDs for virtual flash.• Avoid formatting the SSD disk with VMFS during ESXi installation or Auto Deploy. See “PreventingSSD Formatting During Auto-Partitioning,” on page 170.• If the SSD that you plan to use with virtual flash is formatted with VMFS, remove the VMFS datastore.See “Remove VMFS Datastores in the vSphere Web Client,” on page 146.• To use the SSD disk as virtual flash resource, do not claim this disk for Virtual SAN. If the disk isclaimed by Virtual SAN, remove the disk group that uses the SSD disk. The SSD disk is released fromVirtual SAN and becomes available on the list of disks to us with virtual flash. See “Remove Disks fromVirtual SAN,” on page 185.A local SSD might be unavailable because ESXi cannot recognize it. See “Local SSDs Are Undetectable,” onpage 171VMware, Inc. 209