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

vSphere Storage• “Creating a Diagnostic Partition,” on page 149• “Checking Metadata Consistency with VOMA,” on page 151• “Configuring VMFS Pointer Block Cache,” on page 152Understanding VMFS DatastoresTo store virtual disks, ESXi uses datastores, which are logical containers that hide specifics of physicalstorage from virtual machines and provide a uniform model for storing virtual machine files. Datastoresthat you deploy on block storage devices use the vSphere VMFS format, a special high-performance filesystem format that is optimized for storing virtual machines.Several versions of the VMFS file system have been released since its introduction. The following tableshows host-to-VMFS version relationships.Table 16‐1. Host access to VMFS versionVMFS ESX/ESXi 3.x host ESX/ESXi 4.x host ESXi 5.x hostVMFS2 RO RO NVMFS3 RW RW RWVMFS5 N N RW• RW: Complete read and write support. You can create and power on virtual machines.• RO: Read only support. You cannot create or power on virtual machines.• N: No access. ESXi 5.x does not support VMFS2. If your datastore was formatted with VMFS2, firstupgrade the datastore to VMFS3 using legacy hosts and the vSphere Client.Use the vSphere Web Client to set up a VMFS datastore in advance on a block-based storage device thatyour ESXi host discovers. A VMFS datastore can be extended to span several physical storage extents,including SAN LUNs and local storage. This feature allows you to pool storage and gives you flexibility increating the datastore necessary for your virtual machines.You can increase the capacity of a datastore while virtual machines are running on the datastore. This abilitylets you add new space to your VMFS datastores as your virtual machine requires it. VMFS is designed forconcurrent access from multiple physical machines and enforces the appropriate access controls on virtualmachine files.How VMFS5 Differs from VMFS3VMFS5 provides many improvements in scalability and performance over the previous version.VMFS5 has the following improvements:• Greater than 2TB storage devices for each VMFS extent.• Support of virtual machines with large capacity virtual disks, or disks greater than 2TB. Because VMFS3datastores do not support large capacity virtual disks, you cannot move virtual disks greater than 2TBfrom a VMFS5 datastore to a VMFS3 datastore.• Increased resource limits such as file descriptors.• Standard 1MB file system block size with support of 2TB virtual disks.• Greater than 2TB disk size for RDMs.• Support of small files of 1KB.• Any file located on a VMFS5 datastore, new or upgraded from VMFS3, can be opened in a shared modeby a maximum of 32 hosts. VMFS3 continues to support 8 hosts or fewer for file sharing. This affectsVMware products that use linked clones, such as View Manager.134 VMware, Inc.