Virtualization
describes a technology in which an application, guest OS or data storages is
abstracted away from the true underlying hardware or software.
Key use of
virtualization technology is server virtualization.
The
performance of the virtual system is not equal to the performance of the OS
running on the true hardware; the concept of virtualization works because most
guest OS and application don’t need the full use of the underlying hardware.
This allows
for greater flexibility, control and isolation by removing the depending on n a
given hardware platform.
Whilst
initially mean for server virtualization, the concept of virtualization has
spread to applications, networks, data and desktops.
KVM:
Kernel-based
Virtual Machine (KVM) is a free, open source virtualization architecture for
Linux distributions.
KVM
virtualization, which is supported by RedHat; uses Type-2 hypervisor that
resides within the Linux kernel. KVM
virtualization is often compared with Xen.
Hypervisor:
A
hypervisor is a function which abstracts-isolates -OS and applications from the
underlying computer hardware. This
abstraction allows the underlying host machine hardware to independently
operate one or more virtual machines as guests, allowing multiple guest VMs to
effectively share the system’s physical compute resources, such as processor
cycles, memory space, network bandwidth and so on.
A hypervisor is sometimes also called a virtual Machine Monitor (VMM).
A
hypervisor makes the underlying hardware details irrelevant to the VMs. This allows any VMs to be moved or migrated
between any local or remote virtualized servers – with sufficient computing
resources available – almost at- will with effectively zero disruption to the
VM; a feature often termed as “Live Migration”.
VMs are
also logically isolated from each other, even though they run on the same
physical machine.
In effect,
a VM has no native knowledge or dependence on any other VMs. An error, crash or malware attack on one VM
does not proliferate to other VMs on the same or other machines. This makes hypervisor technology extremely
secure.
Types:
Type-1:
Bare Metal
Type-2:
Hosted
Type-1/Bare
Metal:
Hypervisors
are deployed directly a top the system’s hardware without any underlying OS or
other software. These are called “Bare
Metal” hypervisors and are the most common and popular type of hypervisor for
the enterprise data center.
Eg: VSphere
or Hyper-V
Type-2/Hosted:
Hypervisors
runs as a software layer atop a host OS and are usually called “Hosted”
hypervisors like VMware. Hosted hypervisors are often found on end points like
PCs.
The role of
hypervisor is expanding.
Storage
Hypervisors are used to virtualize all of the storage resources in the
environment to create centralized storage pools that administrators can provision,
without having to concern themselves with where the storage was physically
located.
Networks
are also being virtualized with hypervisors, allowing networks and network
devices to be created, changes, managed and destroyed entirely through software
without ever touching physical network devices.
Solaris Zones:
Zones is a
software partitioning technology that enables the creation and management of
multiple virtualized OS execution environments within a single instance of the
Solaris Kernel. Each zone (virtualized
environment) appears as a system to the processes, users, and administrators
within the zone and is isolated from other zones running within the same kernel
instance.
Note:
theoretically/ conceptually – The upper limit for the number of zones on a
system is 8192.
The
isolation provides security, since processes running in one zone are not
visible to the processes running in other zones in the same kernel
instance. The only exception to this is
the global zone, which is the primary zone that represents the Solaris kernel
instance. All processes running in all
zones in a kernel instance are visible to the global zone.
Zones also
provide a resource management container, such that zones created to run
specify applications (webserver, database server etc) can be configured to use
a subset of the hardware resources available on the system.
Caution:
Some refer
to Zones and Containers interchangeably as if they mean exactly the same
thing. This is incorrect because
containers is a technology that comprises the resource management features,
such as resource pools and solaris zones.
Solaris zones is a subset of containers, so the two terms should not be
used interchangeably.
Containers:
1. Containers = Zones + SRM (Solaris
Resource Management)
2. Containers is a technology that
comprises the resource management features, such as resource pools and solaris
zones
3. Remember solaris containers use the
same kernel structure.
Resource Management:
1. One of the integral component of
Soalris10 containers technology.
2. Allows us to perform –
a. Allocate specific computer resource,
such as CPU times & memory
b. Monitor how resource allocations are
being used and adjust the allocation when required.
c. Generates more detailed accounting
information
d. A new resource capping daemon (rcapd)
by a project. [Remember, a project can be number of processes/users].
Consolidation:
1. Resource Management feature of
Solaris containers is extremely useful when a need of consolidating a number of
applications to run on a single server.
2. Reduces cost, complexity of having
to manage numerous separate systems.
3. Consolidate applications onto fewer,
larger, more scalable servers, and also segregate the work load to restrict the
resources that each can use.
4. Via Resource Management feature,
multiple workloads can now be run on a single server, providing an isolated
environment for each, so that one workload cannot affect the performance of the
other.
5. Resource pools can be utilized to
group applications, functions, together and control their resource usage globally,
such as the maximum amount of CPU resource or memory. Additionally, the resource management feature
can tailor the behavior of the Fair Share Scheduler (FSS) to give priority to
specific applications. This is very
useful if, to allocation additional resources to a group of resources for a
limited period of time.
Before Resource
Management, was introduced, this would have meant that a larger server would be
needed to accommodate the resource requirement; even though it only would be used to its capacity once in a
month. Now the resources can be
allocated accordingly to priority, allowing the server to be more effectively
utilized.
LDOM:
1. In virtualization terminology,
Logical DOMains (LDOM) is a technology for server virtualization that enable users
to allocate system resources, such as memory or devices into logical groupings
in order to create multiple virtual machines.
2. Each of the these virtual machines
can use its own OS, have its own resources and also be identified as a single
stand-alone unit within the computer system.
3. LDOM is a free Sun virtualization
technology and is supported on Sun servers which utilize Ultra SPARC T1 or
Ultra SPARC T2 processors, running at least Solaris 10 11/06 and the latest
server firmware.
4. LDOMs make use of a hypervisor as a
layer of abstraction between real, physical hardware and virtual hardware. This virtual hardware is then used to create
number of guest system which can behave very similar to a system running on
bare metal.
5. Importantly, each has its own OBP,
each will install its own copy of the Solaris OS and each will see a certain
amount of CPU, memory, disk and network resources available to it.
6. Unlike some other Type1 hypervisors
running on X86 hardware, the SPARC hypervisor is embedded in the system firmware
and makes both of supporting functions in the Sun4V SPARC instruction set as
well as the overall CPU architecture to fulfill its function
