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infraStructure SerViceS

VMware vStorage

VMware vStorage includes a number of advanced features to efﬁciently manage and use storage

in virtualized environments while trying to hide the complexities of the underlying storage sys-

tems. The key features include the following:

VMware vStorage

•u Virtual Machine File System (VMFS) is a custom-designed cluster ﬁle

system speciﬁcally optimized to store and manage virtual machines. It allows the efﬁcient

sharing of back-end storage by multiple ESX servers and is the key enabler for VMware

features such as VMotion, Storage VMotion, DRS, VMware High Availability, and Fault

Tolerance.

VMware vStorage

•u thin provisioning enables you to over-commit storage capacity similar to

CPU and RAM over-commitment. Thin provisioning initially allocates only as much stor-

age capacity as needed and grows as more data is stored in the virtual disk. This increases

storage utilization allowing you to defer storage purchases until they are really required.

This can signiﬁcantly reduce an organization’s storage budget.

vSphere introduces a high-performance,

•u paravirtualized SCSI (PVSCSI) storage adapter that

offers greater throughput and lower CPU utilization for virtual machines. This is best suited

for environments that run very I/O-intensive guest applications.

VMware vStorage offers APIs for data protection, multipathing, and storage replication

•u

adapters so that storage partners can integrate their solutions with vSphere.

In the next sections, we will discuss each of these vStorage services in detail.

Vi r t u a l Ma c h i n e Fi l e Sy S t e M

VMware created a cluster ﬁle system, VMFS, specially designed to store and manage virtual

machines. VMFS is optimized to support large ﬁles associated with virtual disks, thus enabling

encapsulation of an entire virtual machine in a set of ﬁles. Using VMFS, you can place these vir-

tual machine ﬁles on a shared storage and allow multiple ESX servers to concurrently read and

write to this shared storage.

By managing concurrent access to the shared back-end storage, VMFS enables the foundation

for key VMware features such as VMotion, Storage VMotion, DRS, VMware High Availability,

and Fault Tolerance. As virtual machines are migrated to or restarted on different ESX servers,

VMFS ensures that individual ESX servers are not single points of failure and helps DRS to bal-

ance resource utilization across multiple servers. VMFS uses on-disk ﬁle locking to ensure that

the same virtual machine is not powered on by multiple servers at the same time.

VMFS also acts a logical volume manager by providing an interface to different types of

storage such as Fibre Channel SAN, iSCSI SAN, and NAS. VMFS hides the complexities of under-

lying storage systems and, irrespective of the storage type, simpliﬁes storage management using

automatic discovery and mapping of LUNs to a VMFS volume. You can connect or disconnect a

VMware ESX server from a VMFS volume without impacting other VMware ESX hosts. vSphere

also adds dynamic growth capabilities to VMFS without the need for any downtime. These new

capabilities include hot expansion of VMFS volumes and virtual disks stored in VMFS.

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