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

Chapter 19 Working with Virtual SAN3 Under Virtual SAN, select General and click Edit.4 Deselect the Turn On Virtual SAN check box.Managing Disk GroupsOn each ESXi host that contributes its local disks to a Virtual SAN cluster, disks are organized into diskgroups. A disk group is a main unit of storage on a host. Each disk group includes one SSD and one ormultiple HDDs.Virtual SAN uses an aggregation of disk groups to back up a single datastore that is created when youenable Virtual SAN.When you have multiple SSDs and HDDs on a host, you can have up to five disk groups per host, each diskgroup with up to seven HDDs. In the disk group, the SSD primarily serves as a read cache write buffer,while the HDDs are used for long-term persistent storage. Typically, a higher SSD to HDD ratio, both in sizeand quantity, improves performance.Depending on the mode you select when enabling Virtual SAN on a cluster, you can use different ways toorganize disks into groups.Automatic ModeManual ModeVirtual SAN claims all available and usable disks and organizes them intodefault groups with one SSD and one or multiple HDDs. If you add moredisks to hosts or add new hosts to the Virtual SAN cluster, all applicabledisks are claimed by Virtual SAN. Virtual SAN in automatic mode claimsonly local disks on the ESXi hosts in the cluster. You can add any remotenonshared disks manually.You must specify hosts and disks on the hosts to be used for the Virtual SANdatastore. You have two methods of organizing disks into disk groups, semiautomaticand manual.When you use the semi-automatic method, Virtual SAN organizes the disksthat you specify into default disk groups.Another option is to manually create user-defined disk groups and selectdisks for each group. When you create a disk group manually, your mainconsideration should be the ratio of SSD to HDD capacity. Although theratios depend on use cases and workloads, the best practice is to use 1:10ratio of SSD capacity to HDD. For example, if the size of your SSD disk is400GB, the aggregated capacity of HDD disks should be 4TB.Virtual SAN disks cannot be used by other features, such as RDM, VMFS, diagnostic partition, and so on.Use Semi-Automatic Method to Claim Disks for Virtual SANWhen Virtual SAN is enabled in the manual mode for the host cluster, you must select SSD and HDD disksto be claimed by Virtual SAN. After you select the disks, Virtual SAN organizes the disks into default diskgroups. This is a semi-automatic method of creating disk groups.Procedure1 Browse to the Virtual SAN cluster in the vSphere Web Client navigator.2 Click the Manage tab and click Settings.3 Under Virtual SAN, click Disk Management.4 Click the Claim Disks icon.VMware, Inc. 183