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Huawei SAN Storage Host Connectivity Guide for VMware ESXi

HUAWEI SAN Storage Host Connectivity Guide for VMware ESXi Servers

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File Systems in VMware

File Systems in VMware

VMFS is a clustered file system that leverages shared storage to allow multiple physical hosts to read and write to the same storage simultaneously. It lays a solid foundation for the management of VMware clusters and dynamic resources.

Features of VMFS

  • Automated maintenance directory structure
  • File locking mechanism
  • Distributed logical volume management
  • Dynamic capacity expansion
  • Clustered file system
  • Journal logging
  • Optimized VMs' file storage

Advantages of VMFS

  • Improved storage utilization
  • Simplified storage management
  • ESX server clusters of enhanced performance and reliability

Architecture of VMFS

In the VMFS architecture shown in Figure 2-3, a LUN is formatted into a VMFS file system, whose storage space is shared by three ESX servers each carrying two VMs. Each VM has a Virtual Machine Disk (VMDK) file that is stored in a directory (named after a VM) automatically generated by VMFS. VMFS adds a lock for each VMDK to prevent a VMDK from being accessed by two VMs at the same time.

Figure 2-3 VMFS architecture

Structure of a VMFS Volume

Figure 2-4 shows the structure of a VMFS volume. A VMFS volume consists of one or more partitions that are arranged in lines. Only after the first partition is used out can the following partitions be used. The identity information about the VMFS volume is recorded in the first partition.

Figure 2-4 Structure of a VMFS volume

VMFS divides each extent into multiple blocks, each of which is then divided into smaller blocks. This block-based management is typically suitable for VMs. Files stored on VMs can be categorized as large files (such as VMDK files, snapshots, and memory swap files) and small files (such as log files, configuration files, and VM BIOS files). Large and small blocks are allocated to large and small files respectively. In this way, storage space is effectively utilized and the number of fragments in the file system is minimized, improving the storage performance of VMs.

The VMFS-3 file system supports four data block sizes: 1 MB, 2 MB, 4 MB, and 8 MB. Sizes of files and volumes supported by VMFS-3 file systems vary with a file system's block size.

The VMFS-5 file system uses a fixed data block size of 1 MB. Supporting VMFS-5, VMware ESXi 5.0/5.1 supports a maximum VMDK file size of 2 TB, and VMware ESXi 5.5/6.0/6.5/6.7 supports a maximum VMDK file size of 62 TB.

The VMFS-6 file system also uses a fixed data block size of 1 MB. Supporting VMFS-6, VMware ESXi 6.5/6.7 supports a maximum VMDK file size of 62 TB.

Updated: 2020-01-17

Document ID: EDOC1000144883

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