1.
What
is the need for VCS?
Version Control System (VCS) are a
category of software tools that help a software team manage changes to source
code overtime. This keeps track of every modification to the code in a special
kind of database. Here sue to due to any case an error occurred developers can
fix them while minimizing disruption to all team members. Simply this is a
system that records changes to a file or set of files overtime so that you can
recall specific version later.
2. Differentiate the three
models of VCSs, stating their pros and cons
Local version control system
There is a risk of loosing everything
when there is a hard-disk failure though the entire history of the project
saved. This is a kind of oldest VSC. This cannot used for collaborative
software development. Here local database is managing on the system itself.
Centralized version control system
This set up offer many advantages especially
over local VCSs. For example everyone knows to a certain extend what each
members doing on the project. Administrators have access who can do what and
it’s far easier to administer a centralized version control system than it is
to deal with local database on every client.
When dealing with negative side of
this due to any reason of the centralized server get down nobody can
collaborate at all or save versioned changes to anything there working on. If
the hard-disk where the central database is on becomes corrupted and proper
backups haven’t been keep, it might loose absolutely everything.
Distributed version control system
Here clients don’t just check the
latest snapshot of the files rather they fully mirror the repository including
it’s s full history. If any server dies & these systems here collaborating
via that server, any of the client repositories can be copied back to the
server to restore it. Every clone is a full back up of all the data. Here we
can deal with several remote repositories so that we can collaborate with
different groups of people in different way in the same project.
This allows to setup several types of
workflows that aren’t possible in centralized system such like hierarchical
models.
3. Git and GitHub, are they
same or different? Discuss with facts.
Git is a version
control system(VCS) that keeps track of all the changes to your project files,
allowing you to work with your team on the same code while saving you a lot of
confusion that tends to happen when multiple people are editing some files. Git
stores every record of every change that you or someone else makes to the
project & this makes keeping track of your progress easy. If you need to
look at your old code, or if you need to see what or who modified it the record
is always there.
GitHub act as remote
storage for your git repository & provides a really neat & simple way
for people to collaborate & contribute to development projects. If you are
looking for ways to contribute to open source, github is the place to go. If
you are new to development, you can use github as a learning tool by analyzing
popular code repositories.
4. Compare and contrast the Git
commands, commit and push ?
Git commit records changes to the
repository and this used in connection with your local repository.
Git push updates remote refs alone
with associated objects and this used to interact with a remote repository.
Since git is a distributed version
control system, the difference is that commit will commit changes to your local
repository, where as push will push changes up to a remote repository. Git
commit record your changes to the local repository.
5. Discuss the use of staging
area and Git directory
Staging Area
Staging area is a place where you hold
temporary tables on data warehouse server. Staging table are connected to work
area or fact tables. We basically need staging area to hold the data and
perform data cleansing and merging before loading the data in to warehouse.
A staging area is like a large table
with data separated from their sources to be loaded into a data warehouse in
the required format. If we attempt to load data directly from OLTP, it might
mess up the OLTP because of format changes between a warehouse and OLTP.
Keeping the OLTP data intact is very important for both the OLTP and the
warehouse.
According to the complexity of the
business rule, we may require staging area, the basic need of staging area is
to clean the OLTP source data and gather in a place. Basically it’s a temporary
database area. Staging area data is used for the further process and after that
they can be deleted.
Staging area is a temp schema used to
u Do flat mapping
Ex: Dumping all the OLTP data in to it
without applying any business rules. Pushing data into stying will take less
time because there are no business rules or transformation applied on it.
u Used for data
cleansing & validations using first layer
In the absence of staging area the
data load will have to go from the OLTP
system to the OLAP system directly, which in fact will severely hamper the performance
of OLTP system. This is the primary reason for the existence of a staging area.
In addition, it also offers a platform for carrying out data cleansing.
Git Directory
The purpose of git is to manage a
project or a set of files as they change over time. Git stores this information
in a data structure called repository. A git repository contains among other
things
1. A set of commit objects
2. A set of reference to commit object called
heads.
The git repository is stored in the
same directory as the project itself, in a sub directory called .git.
There is only one .git directory in
the root directory of the project. The repository is stored in files alongside
the project. There is no central server repository.
6. Explain the collaboration workflow of Git, with example
GitHub flow is a
lightweight, branch-based workflow that supports teams and projects where
deployments are made regularly. This explain how it flows.
CREATE A BUNCH
When you're working
on a project, you're going to have a bunch of different features or ideas in
progress at any given time – some of which are ready to go, and others which
are not. Branching exists to help you manage this workflow.
When you create a branch in your project, you're creating an
environment where you can try out new ideas. Changes you make on a branch don't
affect the master branch, so you're
free to experiment and commit changes, safe in the knowledge that your branch
won't be merged until it's ready to be reviewed by someone you're collaborating
with.
PROTIP
Branching is a core concept in Git, and the entire GitHub flow
is based upon it. There's only one rule: anything in the
master branch is always deployable.
Because of this, it's extremely important that your new branch
is created off of master when working on a feature or a fix. Your branch name
should be descriptive so that others can see
what is being worked on.
7. Discuss the benefits of CDNs
CDN is an interconnected system of
computers on the internet that provides web content rapidly to numerous users
by duplicating or caching the content on multiple servers & directing the
content to users on proximity. The goal of a CDN is to serve content to end
users with high availability & high performance.
CDN serve a large fraction of the
internet content today including web objects, downloadable objects,
applications, real-time streaming data, on demand streaming media & social
networks.
When an end user requests a specific
web page, video or file the server closet to that user is dynamically
determined & is used to deliver the content to that user, thereby
increasing the speed of delivery. Content may be replicated on hundreds or
thousands of servers in order to provide identical content as many users as
possible even during peak time.
Advantages of CDN
Companies that witness a huge traffic
on their website on daily basis can use CDN to their advantage. When a large
number of users simultaneously access a web page on some specific content such
as a video, a CDN enables that content to be sent to each of them without
delay. Here are few of the benefits of using a CDN for your website:
1. Your Server Load will decrease:
As a result of, strategically placed servers
which form the backbone of the network the companies can have an increase in
capacity and number of concurrent users that they can handle. Essentially, the
content is spread out across several servers, as opposed to offloading them
onto one large server.
2. Content Delivery will become
faster:
Due to higher reliability, operators
can deliver high-quality content with a high level of service, low network
server loads, and thus, lower costs. Moreover, jQuery is ubiquitous on the web.
There’s a high probability that someone visiting a particular page has already
done that in the past using the Google CDN. Therefore, the file has already
been cached by the browser and the user won’t need to download again.
3. Segmenting your audience becomes
easy:
CDNs can deliver different content to
different users depending on the kind of device requesting the content. They
are capable of detecting the type of mobile devices and can deliver a
device-specific version of the content.
4. Lower Network Latency and packet
loss:
End users experience less jitter and
improved stream quality. CDN users can, therefore, deliver high definition
content with high Quality of Service, low costs, and low network load.
5. Higher Availability and better
usage analytics:
CDNs dynamically distribute assets to
the strategically placed core, fallback, and edge servers. CDNs can give more
control of asset delivery and network load. They can optimize capacity per
customer, provide views of real-time load and statistics, reveal which assets are
popular, show active regions and report exact viewing details to customers.
CDNs can thus offer 100% availability, even with large power, network or
hardware outages.
6. Storage and Security:
CDNs offer secure storage capacity for
content such as videos for enterprises that need it, as well as archiving and
enhanced data backup services. CDNs can secure content through Digital Rights
Management and limit access through user authentication.
8. How CDNs differ from web
hosting servers?
Difference between CDNs and web
hosting is that web hosting is used to host your website on a server and let
users access it over the internet. Web hosting normally refers to one server. A
content delivery network refers to a global network of edge servers which
distributes your content from a multi host environment.
Web Hosting is used to host your
website on a server and let users access it over the internet. A content
delivery network is about speeding up the access/delivery of your website’s
assets to those users.
Traditional web hosting would deliver
100% of your content to the user. If they are located across the world, the
user still must wait for the data to be retrieved from where your web server is
located. A CDN takes a majority of your static and dynamic content and serves
it from across the globe, decreasing download times. Most times, the closer the
CDN server is to the web visitor, the faster assets will load for them.
Web Hosting normally refers to one
server. A content delivery network refers to a global network of edge servers
which distributes your content from a multi-host environment.
10. Discuss the requirements
for virtualization
1. Different platforms
2. Missing dependencies
3. Wrong configurations.
11. Discuss and compare the
pros and cons of different
virtualization techniques in different levels
Advantages of
Virtualization
1.Using Virtualization for Efficient
Hardware Utilization
Virtualization
decreases costs by reducing the need for physical hardware systems. Virtual
machines use efficient hardware, which lowers the quantities of hardware,
associated maintenance costs and reduces the power along with cooling the
demand. You can allocate memory, space and CPU in just a second, making you
more self-independent from hardware vendors.
2. Using Virtualization to Increase
Availability
Virtualization
platforms offer a number of advanced features that are not found on physical
servers, which increase uptime and availability. Although the vendor feature
names may be different, they usually offer capabilities such as live migration,
storage migration, fault tolerance, high availability and distributed resource
scheduling. These technologies keep virtual machines chugging along or give
them the ability to recover from unplanned outages.
3.Disaster Recovery
Disaster
recovery is very easy when your servers are virtualized. With up-to-date
snapshots of your virtual machines, you can quickly get back up and running. An
organization can more easily create an affordable replication site. If a
disaster strikes in the data center or server room itself, you can always move
those virtual machines elsewhere into a cloud provider. Having that level of
flexibility means your disaster recovery plan will be easier to enact and will
have a 99% success rate.
4.Save Energy
Moving
physical servers to virtual machines and consolidating them onto far fewer
physical servers’ means lowering monthly power and cooling costs in the data
center. It reduces carbon footprint and helps to clean up the air we breathe.
Consumers want to see companies reducing their output of pollution and taking
responsibility.
5.Deploying Servers too fast
You
can quickly clone an image, master template or existing virtual machine to get
a server up and running within minutes. You do not have to fill out purchase
orders, wait for shipping and receiving and then rack, stack, and cable a
physical machine only to spend additional hours waiting for the operating
system and applications to complete their installations. With virtual backup
tools like Veeam, redeploying images will be so fast that your end users will
hardly notice there was an issue.
6.Save Space in your Server Room or
Datacenter
Imagine
a simple example: you have two racks with 30 physical servers and 4 switches.
By virtualizing your servers, it will help you to reduce half the space used by
the physical servers. The result can be two physical servers in a rack with one
switch, where each physical server holds 15 virtualized servers.
7.Testing and setting up Lab Environment
While
you are testing or installing something on your servers and it crashes, do not
panic, as there is no data loss. Just revert to a previous snapshot and you can
move forward as if the mistake did not even happen. You can also isolate these
testing environments from end users while still keeping them online. When you
have completely done your work, deploy it in live.
8.Possibility to Divide Services
If
you have a single server, holding different applications this can increase the
possibility of the services to crash with each other and increasing the fail
rate of the server. If you virtualize this server, you can put applications in
separated environments from each other as we have discussed previously.
Disadvantages of
Virtualization
1.
Extra
Costs
Maybe
you have to invest in the virtualization software and possibly additional
hardware might be required to make the virtualization possible. This depends on
your existing network. Many businesses have sufficient capacity to accommodate
the virtualization without requiring much cash. If you have an infrastructure
that is more than five years old, you have to consider an initial renewal
budget.
2.
Software
Licensing
This
is becoming less of a problem as more software vendors adapt to the increased
adoption of virtualization. However, it is important to check with your vendors
to understand how they view software use in a virtualized environment.
3.
Learn the
new Infrastructure
Implementing
and managing a virtualized environment will require IT staff with expertise in
virtualization. On the user side, a typical virtual environment will operate
similarly to the non-virtual environment. There are some applications that do
not adapt well to the virtualized environment.
Desktop virtualization
Desktop
virtualization is an increasingly important technology for many organizations.
A virtual desktop means that a user’s desktop environment is stored remotely on
a server, rather than on a local PC or other client computing device.
1.
Cost Savings
From an IT perspective, virtual desktops help reduce the time it takes to provision new desktops, and they also help to decrease desktop management and support costs. Experts estimate that maintaining and managing PC hardware and software accounts for 50-70% percent of the total cost of ownership (TCO) of a typical PC. Companies often turn to virtual desktops to cut these IT labor costs.
From an IT perspective, virtual desktops help reduce the time it takes to provision new desktops, and they also help to decrease desktop management and support costs. Experts estimate that maintaining and managing PC hardware and software accounts for 50-70% percent of the total cost of ownership (TCO) of a typical PC. Companies often turn to virtual desktops to cut these IT labor costs.
2.
Simplified management
Since everything is
centrally managed, stored and secured, virtual desktops eliminate the need to
install, update and patch applications, back up files and scan for viruses on
individual client devices. Desktop virtualization also helps to streamline
management of software assests.
3.
Enhanced Security
Virtual desktops provide
greater security to an organization because employee aren’t carrying around
confidential company data on a personal device that could easily be lost,
stolen or tampered with.
4.
Increased productivity
Virtual desktops allow employees to access
applications and documents from multiple devices, including other desktop
computers, laptops … This increase productivity by allowing workers to access
necessary data from anywhere.
12. Identify popular implementations and available tools
for each level of visualization
Desktop
virtualization generally consists of 5 modules. Those modules consists of
virtual machines on which desktop instance will run, image repository which
hold image data, management server which manages whole infrastructure and users and management console,
finally end user and their connectivity to the network. At the 4th module, Management
console it is provides by management server for end user. End user who want
virtualized remote desktop can log in and make request for the specific or OS
desktop assigned to them. At the 5th , End user module not only
consists of person and end node whish success the virtualized desktop but also
the network which connect that node to the many server and image store.
Tools
: Virtual Box, VM ware server, Parallels, Xen
13. What is the hypervisor and what is the role of it?
Hypervisor
or virtual machine monitor (VMM) is computer software, firmware or hardware
that creates &n run virtual machine. The hypervisor presents the guest
operating system with a virtual operating platform & manages the execution
of the guest operating system
u Provide an environment identical to the
physical environment.
u Provide that environment with minimal
performance cost.
u Retain complete control of the system
resources.
14. How does the emulation is
different from VMs?
Virtual machines make use of CPU iself
–virtualization, to whatever extent it
exists, to provide a virtualizes interface to the real hardware. Emulators
emulate hardware without relying on the CPU being able to run code directly
& redirect some operations to a hypervisor controlling the virtual
content,.
Both aim for some level of
independence from the hardware of the host machine, but a virtual machine tends
to simulate just enough hardware to make the guest work and do so with an
emphasis on efficiency of the virtualization/emulation. Ultimately the VM may
not act like any hardware that really exists and may need VM specific drivers,
but the set of guest drivers will be consistent across a large no: of virtual
environments.
An emulator on the other hand tries to
exactly produce all the behavior including quick and bugs of some real hardware
being simulated.
15.
Compare and contrast the VMs and containers/dockers, indicating their
advantages and disadvantages
|
VMs
|
Containers
|
|
1. Heavy weight
2. Limited performance.
3. Each VM runs in its own OS
4. Hardware level virtualization
5. Start up time in minutes
6. Allocated requirements memory
7. Fully isolated & hence more secure
|
1. Light weight
2. Native performance
3. all containers share the host OS
4. OS virtualization
5. Start up time in milliseconds
6. Requires less memory space
7.Process level isolation, possibly less
secure.
|
Both these have benefits as well as
drawbacks as mentioned in the above table.
VMs are better choice for running apps
that require all the OS resources & functionality, when you need to run
multiple applications or servers or have a wide variety of OS to manage
Containers are a better choice when
your biggest priority is maximizing the number of applications running on a
minimal no: of servers.
