Vmware: VMware Storage Concepts

VMware Storage Concepts

ESXi provides host-level storage virtualization, which logically abstracts the physical storage layer from virtual machines.

An ESXi virtual machine uses a virtual disk to store its operating system, program files, and other data associated with its activities. A virtual disk is a large physical file, or a set of files, that can be copied, moved, archived, and backed up as easily as any other file. You can configure virtual machines with multiple virtual disks.

Storage is one of the most important consideration in Virtualization environment. Storage technology provides a fundamental way to manage VM and helps for performance of VMs.

· Storage improve resource utilization and flexibility

· Simplify management, administration

· Increase uptime and durability

Storage can be either internal or external. Storage may be internal to the server or external like iSCSI, FC, SAN, NAS, etc. It depends on you what type of storage you required based on requirement, budget, etc.

A VM is storage as a set of files in its own directory in a datastore. A datastore is a logical container for storing VM files. datastore can also be used for storing ISO images, VM templates, etc. A datastore is used by vmware as a storage container for files. the datastore could be on a local server or on FC or iSCSI SAN or NFS. Inside the datasotre you will find your virtual machines. When a install an EXSi host on a physical disk of say 500 GB the entire 500GB is used as a datastore on that ESXi host. You can create multiple datastore depending on the number of disk installed on the server or entire storage devices attacted to the network.

VMware datastore support two types of FileSystems

1) VMFS and

2) NFS

In VMware there are two types of disk

1) Physical Disk

2) Virtual Disk

Physical Disk :A Physical disk is a disk which is attached physically to the Host ESXi Server. This disk is directly access as local disk or partition.

Virtual Disk : A Virtual disk is a file or set of files which appears as a physical disk driver to a guest OS. The VD can max of 2 TB.

Virtual Disk Types :

1) RAW Disk

2) Thick Disk

3) Zero Thick Disk

4) Eager Zero Thick Disk

5) Thin Disk

RAW Disk : A raw disk is referred to as raw device mapping(RDM) and it enables a VM to have direct access to LUN on SAN. This means the actual VD is store on LUN and a RDM file is create on host EXSi server.

Thick Disk : All space is allocated at creation time. It means when you create a VD of 40GB an entire 40GB space is reserved from this physical disk. These disk are less secure because, their disk block have bot been cleared of previous data.

Zeroed Thick Disk : All space is allocated at the time of creation and the disk is wiped clean of previous data. As the space is used, data is zeroed out on demand.

Eager Zeroed Thick Disk : All space is allocated at the time of creation and disk is wiped clean of previous data. When this disk is created all data is zeroed out. It takes more time for creation of this disk but are faster when writing data.

Thin Disk : This does not take the entire disk space. It starts small and grows as data is written to the size specified. This disk space disk space and are faster.

VM Files

vmware.log : this files keeps a logs of vmware activities and are used for troubleshooting

.nvram = this files act as BIOS of virtual machine

.vmdk = this is the actual VD which stores VM OS.

.vmx = this file store the configuration setting of a virtual machine

.vmsd = this file store vm snapshot information and metadata

.vmsn = this file store snapshot state of a virtual machine.

Virtual Machine File Systems (VMFS)

VMFS is called as cluster file systems. It was developed and is used to store VM disk images, including snapshots. Multiple server can r/w the same file system simultaneously, while individual VM files are locked.

VMFS Version :

VMFS version 1 = use by ESX 1.x and does not have cluster filesystems

VMFS version 2 = used by ESX 2.x and 3.x.

VMFS version 3 = used by ESX 3.x and vSphere 4.x

VMFS version 5 = used by EXXi 5.x. It introduced a new feature of 1MB block size to support larger file size. It support a file size upto 2 TB.

Limitation of VMFS

Can be shared with up to 64 EXS/EXSi host

Can support LUN with max size of 64TB

The limit of 130690 files can be stored on a single datastore

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Types of Storage device

1) Local Storage

2) Network Storage

Local Storage : Local storage can be internal hard disks located inside your ESXi host. In this example of a local storage topology, the host uses a single connection to a storage disk. On that disk, you can create a VMFS datastore, which you use to store virtual machine disk files.

NOTE : You cannot use IDE/ATA or USB drives to store virtual machines

Local storage devices do not support sharing across multiple hosts. A datastore on a local storage device can be accessed by only one host. Because the majority of local storage devices do not support multiple connections, you cannot use multiple paths to access local storage.

Networked Storage : Networked storage consists of external storage systems that your ESXi host uses to store virtual machine files remotely. Typically, the host accesses these systems over a high-speed storage network. Networked storage devices are shared. Datastores on networked storage devices can be accessed by multiple hosts concurrently.

ESXi supports the following networked storage technologies.

1) Fibre Channel (FC)

2) Internet SCSI (iSCSI)

3) Network Attached Storage (NAS) - NFS

4) Shared Serial Attached SCSI (SAS)

Virtual Machines accessing different types of storage

Display Storage Devices for a Host

Use the vSphere Client to display all storage devices or LUNs available to a host. If you use any third-party multipathing plug-ins, the storage devices available through the plug-ins also appear on the list.

Procedure

1) 1 In Inventory, select Hosts and Clusters.

2) 2 Select a host and click the Configuration tab.

3) 3 In Hardware, select Storage.