System overview

At a Glance
• Server Technology
• Operating System
• Virtualization
• Server Deployment
• Server Management Console
• Server Availability Concepts and Techniques
• Server Workload
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Instructor: Mr.S.Christalin Nelson|SoCSE|UPES
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Server Technology (1/4)
• Server: A device or computer program that can provide
various functionalities (Services) for other devices or
computer programs (Clients).
– This architecture is called the client–server model.
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– Functionalities may be data/resource
sharing among multiple clients, or
performing computation for a client.
– A client process may run on the same
device or may connect over a
network to a server on a different
device.
– A single server can serve multiple
clients & a single client can use
multiple servers.
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• Peer-to-Peer Model
– Each client can function as both client & server simultaneously
to share files and printers as inexpensively as possible. There is
no main server on the network.
– P2P Windows OS
• Win 3.11, Win95, NT Workstation, Win98 and Win2000
Professional.
– Can support about 10 clients (workstations) appropriate only
for very small businesses or for home use.
– Suffers from some serious performance, management and
security problems.
• Security offered at the sharing level is the least and confined
with only access-level passwords.
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• Client server model
– There are an almost infinite variety of client/server networks.
– Have centralized security databases that control access to
shared resources on servers.
– More secure
• Server contains a list of usernames and passwords. Once logged
on by supplying valid credentials, the users may access only the
resources that the network administrator allows them to access.
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• Client server model (contd.)
– Windows servers: NetWare, NT, any Win2000 Server product.
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– More stable
• Shared resources reside on
the server, where they are
safe from curious users.
• Easier to back-up data –
whereas, it is very difficult
to back up in P2P system.
– Downside of Client/Server
Networks
• High Cost (Servers, Client
licenses, trained personnel).
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Server Types (1/6)
• FTP Server
– Provides file management functionalities. FTP makes it
possible to move one or more files securely between systems.
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Server Types (2/6)
• Proxy Server
– Acts as an intermediary between a client and a server to
prevent unauthorized access.
• Firewall vs. Proxy Server: Firewall is used to protect an internal
network against attacks while a Proxy Server is used for
anonymity and to bypass restrictions.
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Server Types (3/6)
• Web Server
– Serves content across the network to a user’s Web browser by
loading a file from a disk. This uses HTTP.
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Server Types (4/6)
• Telnet Server
– Enables user to log on to a host computer and perform tasks as
if working on the remote computer itself.
– It is not secure because data is transferred in plaintext only.
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Server Types (5/6)
• Print Server
– Provides printing functions and share the printer to access in
the network.
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Server Types (6/6)
• Database Server
– Provides the database functionalities running on the server.
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Tower Server (1/2)
• Tower Server is a computer intended for use as a server and
built in an upright standalone cabinet called tower.
– Tower is similar in size & shape to cabinet for a tower-style PC.
• Example
– IBM X Series 235 Tower Server
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Tower Server (2/2)
• Advantages
– Easier cooling, because overall component density is fairly low.
– Scalability, because an unlimited number of servers can be
added to an existing network.
• Disadvantages
– A set of tower servers is bulkier and heavier than an
equivalent blade server or set of rack servers.
– Cabling for a large set of tower servers can be complicated.
– A group of several air-cooled tower servers in a single location
can be noisy because each tower requires a dedicated fan.
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Rack Server (1/2)
• Rack server or rack-mounted server, is a computer dedicated
to use as a server and designed to be installed in a metal
framework called a rack.
– The rack contains multiple mounting slots called bays, each
designed to hold a hardware unit secured in place with screws.
– A single rack can contain multiple servers stacked one above
the other, consolidating network resources and minimizing the
required floor space.
• U is the standard unit of measure of vertical usable space,
height of racks and the cabinets.
– 1U is 19 inches wide and 1.75 inches tall.
– The Rack Server comes with different sizes from 1U to 7U.
• Each rack server has separate power supply.
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Rack Server (2/2)
• Example:
– IBM System x3650 M4 Rack Server
• The rack server configuration also simplifies cabling among
network components.
• In an equipment rack filled with many power-dissipating
components (servers) confined in a small space, a special
cooling system is necessary to prevent excessive heating.
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Blade Servers (1/3)
• A Blade server is a server chassis housing multiple thin,
modular electronic circuit boards, known as server blades.
– Each blade is literally a server on a card often dedicated to a
single application with its own OS, processors, memory,
integrated network controllers, an optional FC HBA and other
IO ports.
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– Individual blades in the
chassis are connected
with Bus system to form
blade server.
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Blade Servers (2/3)
• Blade servers provide more processing power in less rack
space, simplifying cabling and reducing power consumption.
– Provide 85% reduction in cabling over 1U or tower servers.
• The components in the entire cabinet share a common
power supply and cooling system.
• The Components are hot swappable & hot pluggable.
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– i.e. Can be added or replaced without
interrupting (shut down) the operation
of the entire system.
– Software can be installed without any
need of system reboot.
• Example
– IBM BladeCenter H Blade Server
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Blade Servers (3/3)
• Storage
– Each blade comes with one or two local ATA or SCSI drives. For
additional storage, blade servers can connect to a storage pool
facilitated by a NAS or SAN.
– The consolidation of associated resources (like storage and
networking equipment) into a smaller architecture provides a
single interface for ease of management.
• A blade server is sometimes referred to as a high-density
server typically used in clustering of servers that are
dedicated to a single task (File sharing, Web page serving
and caching, Streaming audio and video content).
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Enterprise Servers
• An enterprise server is a computer containing programs that
collectively serve the needs of an enterprise rather than a
single user, department, or specialized application.
– Includes Mainframe-sized computers to even small UNIX -
based servers & Wintel computers.
• An enterprise server is both hardware & main software (OS).
• Examples
– Sun Microsystems' UNIX-based Solaris or Linux systems, HP
systems, upper end of Windows 2000 systems, IBM's iSeries
systems including the largest zSeries 900 (formerly S/390).
• Note:
– How is Micro-Computer, Mini-Computer, Super Computer &
Mainframe computer different from each other?
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High Performance Computing Servers
• High Performance Computing Servers are the most powerful
and flexible computer systems used in research.
• HPC clusters are capable of even outperforming the
supercomputing market.
• Typical HPC systems can deliver industry-leading, cost-
effective performance.
• Applied fields
– Include areas like Climatology, quantum chemistry,
computational medicine, high energy physics.
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Operating System (1/2)
• Operating System (OS) is a System software
used to manage computer hardware and
software resources and provide common
services for functioning of application
programs.
– The OS module which handles resource
allocation is called scheduler.
• The users can interact with OS’s command line
interpreter through a set of commands.
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• Kernel
– A program that constitutes the central core of a computer’s OS.
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Operating System (2/2)
• Examples of modern OS
– Andriod, BSD, iOS, Linux, Windows, IBM z/OS
• Features & Types of OS
– Multi-User OS
– Multiprocessing
– Multitasking systems
– Multiprogramming
– Multithreading
– Real-time OS (RTOS)
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Multi-User systems
• A multi-user OS allows multiple users to access the data and
processes of a single machine from different computers or
terminals.
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Multiprocessing Systems
• Multiprocessing refers to the hardware (i.e., the CPU units)
rather than the software (i.e., running processes).
• The underlying hardware provides more than one processor.
– Variations on the basic scheme
• Multiple cores (independent processing units) on one die/chip.
– Single processor can run multiple instructions on separate cores at
the same time, increasing overall speed for programs.
• Multiple dies in one package.
• Multiple packages in one system.
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Multitasking Systems
• A task refers to a “thread of execution” when one process is
divided into sub-tasks.
• A multitasking OS allows more than one task to run
concurrently on single processor. The illusion of parallelism
is achieved when the CPU is reassigned to another task by
task context switching.
– Each task (does not hijack the CPU until it finishes) takes a fair
share amount of the CPU time called quantum. Hence
multitasking systems are also referred as Time-sharing
systems.
– Note: Pre-emptive & Non-preemptive scheduling.
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Multiprogramming (1/5)
• OS can load multiple programs (which are ready to execute)
in the main memory. But only one program is allocated with
the CPU at a time for executing its instructions. The others
need to wait for their turn.
• Multiprogramming aims to maximize the use of CPU time
(keep the CPU busy as long as there are processes ready to
execute) by the adopting process context switching.
– i.e. If the currently running process is performing an I/O task
(which does not need CPU), the OS may interrupt that process
and give the control to one of the other in-main-memory
programs that are ready to execute.
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• Issues
– If there are N processes ready and highly CPU-bound (i.e., they
mostly execute CPU tasks and none or very few I/O
operations), in the very worst case one program might wait all
the other (N-1) programs until it completes.
– The OS should provide the required protection (after loading in
to separate areas of the main memory) to avoid the chance of
one process being modified by another one.
– Fragmentation (During swapping).
– Large programs may not fit at once in memory. Hence
pagination and virtual memory is required.
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• Virtual Memory (1/3)
– Memory management technique which introduces the concept
of virtual memory address (VMA) space, allowing each process
to think of physical memory as a contiguous address space (or
collection of contiguous segments).
• A VMA space can exceed the actual capacity of main memory by
using secondary memory & thus referencing more memory than is
physically present in the system.
– Two main aspects of implementation
• Paging Supervisor (Software component of kernel) manages VMA
spaces by setting either a single VMA space for all processes or
one space for each process with its mapping.
• A specific hardware on CPU chip (Memory Management Unit or
MMU) maps VMAs (generated during program execution) into
physical addresses in main memory using the TLB or Page table.
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– Every virtual memory implementations divide a VMA space into
blocks of contiguous VMAs, called pages (usually 4 KB).
• OS store mappings between virtual and physical addresses in a
data structure called Page table.
• MMU stores a cache of recently used mappings in TLB.
– Page replacement or Swapping
• Moving pages from/to secondary storage to/from main memory.
• The paging supervisor performs swapping using page replacement
algorithms (e.g. LRU).
– Note:
• Internal Fragmentation: The unused/wasted allocated space when
memory allocated to a process > required memory.
• Internal Fragmentation: The unused/wasted non-contiguous space
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Multithreading systems
• Multithreading allows a single process to have multiple code
segments (i.e., threads) which can be run concurrently
within the “context” of that process.
• Threads can be considered as child processes that share the
parent process resources but execute independently.
– Threads are synchronized by the OS to prevent race conditions
and avoid inconsistency and deadlocks while using shared
resources.
• Multiple threads of a single process can
– Share the CPU in a single CPU system or
– Run in parallel in a multiprocessing system
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Real Time OS (1/2)
• The main concern of RTOS is it produces an accurate output
within the deadline or time.
• The OS divides time into execution units called system ticks,
at every system tick the scheduler is run and it decides
which task should run next.
• A task is allowed to run for the duration of a system tick
unless it is preempted by a higher priority task or it gets
suspended.
• Types
– Soft RTOS
– Hard RTOS
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Real Time OS (2/2)
• Soft RTOS
– A type of OS where certain deadlines may be missed, they will
respond at a time t=0+. Example: Digital camera, PCs
• Hard RTOS
– A type of OS which will respond at a time t=0. They are
constrained to predicted time constraints and deadlines.
– Example: Air bag control in cars, defense system.
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Functions (1/2)
• Process management
– Ensures that each process and application receives the
required processor’s time for its functioning and using as many
processor cycles as possible.
• Process or Thread is a basic unit of software (which performs
actions) that the OS deals with while scheduling the work done
by the processor.
• A process can be controlled by a user, applications or by the OS.
• Memory Management
– A single process must have enough memory to execute.
– Ensures that the various memories in the system are properly
used so that each process can run effectively.
– The operating system sets up the boundary for the types of
software and for individual applications.
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Functions (2/2)
• Device Management
– The driver is a program which acts as a translator between the
electrical signals of the hardware and the high level programming
languages of OS.
– The OS assigns high priority blocks to drivers so as to release and
ready the hardware resource for further usage as quickly as
possible.
• File Management
– The OS uses file system to organize and to keep track of the files.
• The OS makes an entry in the file system to show the start and end
locations of a file, file name, file type, file archiving, and user’s
permissions to read/modify the file and the date and time of the
files creation.
– A hierarchical file system uses directories to organize files into a
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Virtualization and its Benefits
• Virtualization is the technique of splitting one physical
resource into multiple virtual resources or pooling multiple
physical resources into one logical resource.
• A single physical resource can be used for multiple purposes
to perform the required set of actions.
• Benefits
– Reduces hardware cost (One physical resource acts as multiple
virtual resources)
– Workload is optimized (Dynamic resource sharing)
– IT responsiveness and flexibility (Gives a single consolidated
access to all the available resources).
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Types of Virtualization
• Server Virtualization
– Consolidating physical servers into virtual server that run on
many fewer physical servers.
• Desktop Virtualization
– Virtualizing desktops and running them on servers.
• Network Virtualization
– Creating virtual networks inside the software that do not
require any physical network hardware (a must-have for server
virtualization).
• I/O Virtualization (IOV)
– Virtualizing the I/O from the server to peripherals.
– With IOV, physical adapters (NIC, HBA, Disk) are now virtual
adapters (vNIC, vHBA, vDisk) but they work just as the
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I/O Virtualization (1/3)
• IOV decouples network and storage communications from
it’s typical hardware cable path, network/storage switches,
and network/storage adaptors.
• I/O devices are connected within the server using interfaces
or adapter. Adapters take up a lot of server space.
– Once adapters are moved into a switching box
• Devices can be shared across different physical servers.
• Many servers can be accommodated in a single rack.
• In traditional setup, every server has:
– Network: Between 1 to 4+ Ethernet network connections that
require individual NICs, Ethernet cables, and switch ports.
– SAN: A large majority of servers are redundantly connected to
a FC SAN that requires individual HBAs, FC cables, and FC
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• I/O in a traditional server data center scenario
– Requirements
• Multiple I/O adapters per server
• Multiple Network and Storage cables per server
• Multiple Network and Storage switches per rack.25-Aug-2017
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100 servers with only 6
connections/server would
require 600 connections.
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• I/O in a Virtualized server data center scenario
– Consolidate all network and SAN connections onto that single
(or two if redundancy is required) high-speed cable.
Offers huge reduction in
network & storage cabling
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Hypervisor (1/2)
• A technology or software allowing multiple OS to run on a
single hardware at the same time. Hypervisors are also called
as Virtual Machine Manager (VMM).
• Terminology
– Host: Machine and/or software on which VMM is implemented.
– Guest: OS/machine which executes under the control of VMM.
• Types of Hypervisors
– Type 1 & Type 2
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Hypervisor (2/2)
• Features
– Most organizations run their servers in virtual environments in
their data centers. Thus their workload is carried with high
availability and better performance.
– OS and workload can be consolidated into one server, reducing
the cost of operations and hardware.
– Multiple OSs can be run on a single hardware at the same time,
each running applications as per requirements.
– Dynamically assigning of resources is possible from virtual
resource to the physical resource through methods like
dispatching and paging.
– Workload is managed with ease in a single server to improve
the performance, system use and price.
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Type 1 Hypervisor (1/4)
• Type 1 hypervisors run directly on the physical hardware,
without intermediate OS.
• It is also called as “native or bare metal hypervisors” as the
hypervisor itself acts as the OS managing the hardware.
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• VMM contains
– Device drivers: Support disks, graphics
card, file I/O, network I/O, timers, etc.
– Virtual Device Interface: Facilitates
virtualization while presenting the
devices to the VM.
– Resource manager: Manages resource
sharing and establishes isolation barrier
among multiple guest VM domains.
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• These hypervisors provide a layer of hardware virtualization
through which multiple OS can run simultaneously.
• Examples
– Xen
– Oracle VM Server for SPARC, Oracle VM Server for x86
– Citrix XenServer
– Microsoft Hyper-V
– VMware ESX/ESXi
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• Xen Server running NetBSD and 3 Linux Distributions
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• Limitations
– VMware ESXi does not support Windows 8, and would require
the installation of a Type 2 Hypervisor such as Qemu within a
guest OS.
– Xen on the other hand can be quite difficult to configure.
– Hypervisor may or may not be compatible with laptop power
management technologies and drastically affect battery life.
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• Type 2 hypervisor runs over the Operating System using
virtual PC or virtual box.
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• It is also called as a “hosted hypervisor”
as it is installed as a software
application on an existing OS.
• There are two layers between the VM
and Hardware: OS and VMM
• VMM contains
– Virtual device interface layer
– Resource manager
– Do not contain Device drivers and thus
depends on Host OS for device
interactions.
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• Examples
– VMware Workstation, VMware Player
– Virtual Box
– Parallels Desktop for Mac
– QEMU (Quick Emulator)
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Virtual Machine (1/3)
• Virtual machine (VM) is a software which emulates a physical
computing environment, over which OS and programs can be
installed.
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• VMs are generally created
within the virtualization
layer like hypervisor, which
runs over the OS.
• The OS running in the virtual
environment are not aware
of the virtual platform.
• Types of VM
– System VM
– Process VM
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• System VM
– VM provides a complete system platform which supports the
execution of a complete OS.
– System VM or “full virtualization VM” provides a substitute for
a real machine.
• The existing architecture is emulated to suite the purpose of
running the program where the real hardware is not available.
– System VM is also called as “Hardware virtualization”.
– Example:
• Machine in Virtual Box
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• Process VM
– Process VMs runs as a normal application inside a host OS and
are designed to execute computer programs in a platform-
independent environment.
– Provides a platform-independent programming environment that
abstracts away details of the underlying hardware or OS, and
allows a program to execute in the same way on any platform.
– Process VM is also called as “application VM” or MRE (Managed
Runtime Environment).
– Example
• JVM, Wine software in Linux helps to run Windows application.
– Some VMM (such as QEMU) are designed to also emulate
different architectures and allow execution of software
applications written for another architecture.
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Partitioning
• Partitioning physically divides the server into several smaller
servers with dedicated resources.
• Partitioning gives the ability to dedicate a physical computer
to a VM.
• Partitioning was originally implemented by IBM.
• Server partitioning offers a number of distinct advantages to
information technology departments.
• It allows systems administrators to consolidate multiple
applications into one physical server box, which helps to
centralize management, save space and potentially lower
administrative and management costs.
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Server Deployment (1/3)
• Server Deployment is a technology for network-based
installation of the OS/Softwares.
• OS deployment is necessary in the following scenarios:
– Provisioning the OS/Softwares for new employees.
– Redeploying the OS of corrupt systems.
– Periodically redeploying the OS/Softwares according to the
company policies.
• Different ways to deploy an OS
– Standalone Deployment
– Manual Deployment
– Event-driven Deployment
– Scheduled Deployment
– Custom Deployment
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• Standalone Deployment
– Process of deployment on computers that are not a part of the
network.
– This is performed locally using the bootable standalone device.
• Manual Deployment
– Manually change the boot sequence of all the systems to PXE
(Preboot eXecution Environment).
– The OS is deployed using the image that is created.
• Event-Driven Deployment
– Suited in cases where the OS needs to be deployed to multiple
systems simultaneously.
– The OS image is multicast to all the target computers.
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• Scheduled Deployment
– The OS is deployed in multiple systems whose MAC address is
known. Deployment is scheduled by specifying the list of MAC
address.
– The computers are powered on by the administrator using the
Wake-On LAN functionality and the OS image is deployed at
the scheduled time.
• Custom Deployment
– Administrator creates a set of deployment templates which
meets the organization’s needs and assigns a name to each
template.
– The user initiates the deployment by selecting a template by
its name from the boot menu and the deployment process
starts immediately.
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Virtual Server Deployment (1/2)
• Server at someone else’s location that is shared by multiple
website owners so that each owner can use and administer
it as though they had complete control of the server.
• Steps to deploy the Virtual Server
– IIS installation: The www service component of the IIS must be
installed to manage the virtual server.
– Virtual Server installation: A single physical computer or
multiple computers can be used for both the virtual server
service and the administration website components.
– Adding a VM: a VM is added for each of the guest OS.
– Adding guest OS: Guest OS is added to the VM which is
created.
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Virtual Server Deployment (2/2)
• NTFS must be used on the host OS as the Virtual server
security architecture depends on the security feature
provided by the NTFS.
• System requirement depends on
– Number and type of OS
– Applications to be installed on the VMs
– Workload
• Number of VMs supported by the Virtual server depends on
– System resources.
– Amount of memory assigned to each VM (up to 3.6GHz)
– Total available memory on the physical computer.
– Note: Can support a maximum of 64 VMs
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Server Management Console
• The console provides centralized administration and
management of processes in distributed networks.
• Used to perform the following administrative tasks
– Viewing and managing/modifying the server roles and
features installed on the server.
– Starting/stopping the services to perform the management
tasks (life cycle of server, managing local user accounts).
– Identifying critical events, determining the server status and to
analyze and troubleshoot configuration failures.
– Role services, Installing and removing the roles and features
using Windows command line.
• The management of the server manager can also be done
remotely using Remote Server Administration Tool (RSAT).
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Server Availability
• Server Availability is defined as a level of service provided by
applications, services and systems.
• Highly available systems will have minimum downtime.
– A widely held but difficult to achieve standard of availability
for a system or product is known as “five 9’s (99.99999%
availability)”.
• Various systems offer clustering, advanced fault tolerance
and file system recoverability features with high availability.
• Techniques
– Server Clusters and Grid Computing Clusters
– Network Load Balancing
– High Performance Computing
– Few Server Restarts, Downtime
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Server Clusters (1/3)
• Server Cluster is a feature which provides high availability,
scalability and manageability for various applications and
resources.
• Failback process takes place when a failed server
automatically recommences performing its former
operations once it is online again.
• Failover clusters
– The servers (nodes) in the cluster remain in constant
communication, if any one of the node in the cluster fails,
another node begins to provide service.
– Failover cluster uses a voting algorithm to determine whether
the cluster has enough votes to maintain the quorum.
• If the number of votes drops below the majority the cluster stops
running.
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• Failover clusters (contd.)
– Failover clusters use
quorum to ensure that
enough members are
available for the cluster to
continue its operations.
• Quorum prevents two
sets of nodes from
operating
simultaneously (i.e. from
resulting in a partition
within the cluster).
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• Benefits
– Ensure high availability for mission critical applications and
services and the operations of a failed node are immediately
resumed by another node in the cluster.
– Nodes in the cluster are also able to automatically resume its
previous operations if it is brought online again. This basically
means that no manual configuration is necessary to initiate
the failback process.
– Reduce downtime associated with scheduled maintenance
because the operations of one node can be moved to another
node before performing upgrades.
– Enables access to resources and services during planned
downtime. There is no need to interrupt client access.
– Reduce single points of failure on the network because they
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Grid Computing
• Grid computing clusters are identical to the HPC except that
the nodes do not function as a single computational entity.
• Tasks are sent to nodes which perform the work
independently from the rest of the cluster.
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Network Load Balancing
• Network Load Balancing (NLB) improves the scalability and
availability of internet/web server programs and also to
scale up the server performance.
• Benefits
– Scalability: NLB combines the resources of multiple computers
into a single cluster. NLB scales the performance of a server by
distributing its client requests across multiple servers within
the cluster. As traffic increases, additional servers can be
added to the cluster, with up to 32 servers possible in any one
cluster.
– High availability: NLB provides high availability by
automatically detecting the failure of a server and
repartitioning client traffic among the remaining servers
within 10sec, while providing users with continuous service.
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High Performance Computing
• High performance computing clusters spreads the
computational tasks among multiple nodes.
• HPC clusters require active communication between the
cluster servers.
• HPC clusters take the advantage of parallel processing
available with multiple nodes which act as a single
computational entity.
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Few Server Restarts
• Several OSs make configuring hardware and software easier
by performing many activities without a server restart.
– Example: Extension of storage volume, Network protocol
configuration
• Outage: The loss of any computer service to the user.
– The time duration of the outage is called as downtime.
– The downtime can be planned or unplanned.
– Sometimes necessary outages are planned for system upgrade,
moving an application from one system to another and
physical movement of equipment.
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Downtime (1/2)
• Availability = Uptime / (Uptime+Downtime)
• Scheduled downtime is a result of logical or a management
initiated event.
– The scheduled downtime events include system upgrade,
moving an application from one system to another and
physical movement of equipment.
• Unscheduled downtime is an event which typically arises
from any physical event such as a hardware or software
failure.
– Unscheduled downtime happens due to power outages, failed
CPU, over temperature related shutdowns.
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Downtime (2/2)
• A system in order to be highly available is built on highly
reliable components. The requirements for components to
be made highly available are :
– Reliable basic hardware
– Software quality
– System management tools
– Support and maintenance services
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Server Workload (1/2)
• Server Workload is the amount of processing that the server
is assigned at a given time.
– i.e. Amount of application programs running & the users
interacting with the systems applications.
• The workload is specified as a benchmark to evaluate the
server in terms of its performance (divided into response
time and throughput).
– Response time: Time between the user request and the
response to the request.
– Throughput: The amount of work that is accomplished over a
period of time.
• The amount of work handled by the server estimates the
efficiency and performance of that particular server.
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Server Workload (2/2)
• Types of Server Workload
– Memory Workload
– CPU Workload
– IO Workload
– Database Workload
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Memory Workload (1/2)
• Programs or instructions require memory to store data and
perform intermediate computations.
• The amount of memory used by the server over a given
period of time or at a specific instant of time is determined
by the memory workload.
• If the number of programs to be executed becomes large, it
needs more amount of memory which should be effectively
managed.
• The usage of the main memory is increased by the paging
and segmentation process which uses a lot of virtual
memory.
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Memory Workload (2/2)
• Swapping
– Note: Refer content discussed under Virtual Memory.
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CPU Workload
• The number of instructions that is executed by the processor
during a given period of time is indicated by CPU workload.
• More CPU power is needed if the CPU is overloaded always.
• The improvement in performance is obtained for the same
number of instructions by decreasing the number of cycles
required by the instruction.
– During each cycle, a CPU can perform a basic operation such as
• Fetching an instruction
• Accessing memory
• Writing data
– Since only simple commands can be performed during each
cycle, most CPU processes require multiple clock cycles.
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Other types of Server Workload
• I/O Workload
– The number of inputs got by a server and the number of
outputs produced by the server over a particular duration of
time is called as I/O workload.
• Database Workload
– The workload of a database is analyzed by the determination
of the number of queries executed by the database over a
given period of time, or an average number of queries
executed at an instant of time.
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Peep into the next Module
• Directory Services Overview
– Directory Services Concepts
– LDAP Protocol
– LDAP Replication Topologies
– LDAP Data Interchange Format
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System overview

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