Senin, 28 April 2014

CLOUD COMPUTING

Cloud computing is a type of computing that relies on sharing computing resources rather than having local servers or personal devices to handle applications.
In cloud computing, the word cloud (also phrased as "the cloud") is used as a metaphor for "the Internet," so the phrase cloud computing means "a type of Internet-based computing," where different services — such as servers, storage and applications. are delivered to an organization's computers and devices through the Internet.
Cloud computing is comparable to grid computing, a type of computing where unused processing cycles of all computers in a network are harnesses to solve problems too intensive for any stand-alone machine.

The world of the cloud has lots of participants:
·         The end user who doesn’t have to know anything about the underlying technology.
Business management who needs to take responsibility for the governance of data or services living in a cloud. Cloud service providers must provide a predictable and guaranteed service level and security to all their constituents.

·         The cloud service provider who is responsible for IT assets and maintenance.



Advantages of cloud computing

1.  Worldwide Access. Cloud computing increases mobility, as you can access your documents from any device in any part of the world. For businesses, this means that employees can work from home or on business trips, without having to carry around documents. This increases productivity and allows faster exchange of information. Employees can also work on the same document without having to be in the same place.
2.      More Storage. In the past, memory was limited by the particular device in question. If you ran out of memory, you would need a USB drive to backup your current device. Cloud computing provides increased storage, so you won’t have to worry about running out of space on your hard drive.
3.      Easy Set-Up. You can set up a cloud computing service in a matter of minutes. Adjusting your individual settings, such as choosing a password or selecting which devices you want to connect to the network, is similarly simple. After that, you can immediately start using the resources, software, or information in question.
4.      Automatic Updates. The cloud computing provider is responsible for making sure that updates are available – you just have to download them. This saves you time, and furthermore, you don’t need to be an expert to update your device; the cloud computing provider will automatically notify you and provide you with instructions.
5.      Reduced Cost. Cloud computing is often inexpensive. The software is already installed online, so you won’t need to install it yourself. There are numerous cloud computing applications available for free, such as Dropbox, and increasing storage size and memory is affordable. If you need to pay for a cloud computing service, it is paid for incrementally on a monthly or yearly basis. By choosing a plan that has no contract, you can terminate your use of the services at any time; therefore, you only pay for the services when you need them

The working principle of cloud computing

The principle of cloud computing is almost same with another computer,  just the different of that is in cloud computing, is coupled with another present computer.  In regular computer, file from software when we used is stored in hardisk or another storage media. But on computer clouds if viewed from the side of the user, the files from software we use is in another computer.
In other words we are connected to multiple computers on a network server, but the data we store it was in the data center or in center, so that not only we can open the file that we save but computers or other users can open it and vice versa (Public). Also in a lot of infrastructure servers that we can use and we only pay as needed.

 Characteristics cloud computing

1. On-demand self-service. This means provisioning or de-provisioning computing resources as needed in an automated fashion without human intervention. An analogy to this is electricity as a utility where a consumer can turn on or off a switch on-demand to use as much electricity as required.
2. Ubiquitous network accessThis means that computing facilities can be accessed from anywhere over the network using any sort of thin or thick clients (for example smartphones, tablets, laptops, personal computers and so on).
3. Resource pooling. This means that computing resources are pooled to meet the demand of the consumers so that resources (physical or virtual) can be dynamically assigned, reassigned or de-allocated as per the requirement. Generally the consumers are not aware of the exact location of computing resources. However, they may be able to specify location (country, city, region and the like) for their need. For example, I as a consumer might want to host my services with a cloud provider that has cloud data centers within the boundaries of Australia.
4. Rapid elasticity. Cloud computing provides an illusion of infinite computing resources to the users. In cloud models, resources can be elastically provisioned or released according to demand. For example, my cloud-based online services should be able to handle a sudden peak in traffic demand by expanding the resources elastically. When the peak subsides, unnecessary resources can be released automatically.
5. Measured service. This means that consumers only pay for the computing resources they have used. This concept is similar to utilities like water or electricity.

SECURITY

Security. When using a cloud computing service, you are essentially handing over your data to a third party. The fact that the entity, as well as users from all over the world, are accessing the same server can cause a security issue. Companies handling confidential information might be particularly concerned about using cloud computing, as data could possibly be harmed by viruses and other malware. That said, some servers like Google Cloud Connect come with customizable spam filtering, email encryption, and SSL enforcement for secure HTTPS access, among other security measures.

The biggest question most have with Cloud Computing is will it be Safe? The answer is “NO”  Reason why is everything that Cloud Computing is based on is mechanical, although it seems virtual. The Safety of the data (information), is only as Safe as the will and determination of the individual that wants to have at it.

THE CONCEPT OF CLOUD COMPUTING


The first building block is the infrastructure where the cloud will be implemented. Some people make the assumption that environment should be virtualized, but as cloud is a way to request resources in an on-demand way and if you have solutions to provide  on bare metal, then why not? The infrastructure will support the different types of cloud (IaaS, PaaS, SaaS, BPaaS).
To be able to provide these services you will need Operating System Services (OSS), which will be in charge of deploying the requested service, and Business System Services (BSS), mainly used to validate the request and create the invoice for the requested services. Any metrics could be used to create the invoice (for example, number of users, number of CPUs, memory, usage hours/month). It is very flexible and depends on the service provider.
A cloud computing environment will also need to provide interfaces and tools for the service creators and users. This is the role of the Cloud Service Creator and Cloud Service Consumer components.
Now, let’s see how it works in reality.
Generally, you log in to a portal (enterprise or public wise) and you order your services through the Cloud Service Consumer. This service has been created by the cloud service provider and can be a simple virtual machine (VM) based on an image, some network components, an application service such as an WebApp environment and a service such as MongoDB. It depends on the provider and type of resources and services.
The cloud provider will validate, through the BSS, your request and if the validation is okay (credit card, contract), it will provision the request through the OSS.
You will receive, in one way or another, the credentials to access your requested services and you will usually receive a monthly invoice for your consumption.


http://thoughtsoncloud.com/2014/02/how-does-cloud-computing-work/
http://thoughtsoncloud.com/2014/02/cloud-computing-basics/
http://www.dummies.com/how-to/content/what-is-cloud-computing.html
http://www.wikinvest.com/concept/Cloud_Computing
http://www.webopedia.com/TERM/C/cloud_computing.html

Selasa, 15 April 2014

Sistem Operasi Terdistribusi

2. Sistem Operasi Terdistribusi
A. Pengertian Sistem Operasi
     Sistem operasi (Operating System atau OS) adalah perangkat lunak sistem yang bertugas untuk melakukan kontrol dan manajemen perangkat keras serta operasi-operasi dasar sistem, termasuk menjalankan software aplikasi seperti program-program pengolah kata dan browser web.
     Secara umum, Sistem Operasi adalah software pada lapisan pertama yang ditaruh pada memori komputer pada saat komputer dinyalakan. Sedangkan software-software lainnya dijalankan setelah Sistem Operasi berjalan, dan Sistem Operasi akan melakukan layanan inti umum untuk software-software itu. Layanan inti umum tersebut seperti akses ke disk, manajemen memori, skeduling task, dan antar-muka user. Sehingga masing-masing software tidak perlu lagi melakukan tugas-tugas inti umum tersebut, karena dapat dilayani dan dilakukan oleh Sistem Operasi. Bagian kode yang melakukan tugas-tugas inti dan umum tersebut dinamakan dengan "kernel" suatu Sistem Operasi.
Sistem Operasi secara umum terdiri dari beberapa bagian:
1. Mekanisme Boot, yaitu meletakkan kernel ke dalam memory
2. Kernel, yaitu inti dari sebuah Sistem Operasi
3. Command Interpreter atau shell, yang bertugas membaca input dari pengguna
4. Pustaka-pustaka, yaitu yang menyediakan kumpulan fungsi dasar dan standar yang dapat dipanggil oleh aplikasi lain
5. Driver untuk berinteraksi dengan hardware eksternal, sekaligus untuk mengontrol mereka.


B. Komponen Sistem Operasi
Komponen sistem operasi terdiri dari:
a. Manajemen Proses
Proses adalah keadaan ketika sebuah program sedang di eksekusi. Sebuah proses membutuhkan beberapa sumber daya untuk menyelesaikan tugasnya. sumber daya tersebut dapat berupa CPU time, memori, berkas-berkas, dan perangkat-perangkat I/O. Sistem operasi bertanggung jawab atas aktivitas-aktivitas yang berkaitan dengan manajemen proses seperti:
• Pembuatan dan penghapusan proses pengguna dan sistem proses.
• Menunda atau melanjutkan proses.
• Menyediakan mekanisme untuk proses sinkronisasi.
• Menyediakan mekanisme untuk proses komunikasi.
• Menyediakan mekanisme untuk penanganan deadlock.
b. Manajemen Memori Utama
Memori utama atau lebih dikenal sebagai memori adalah sebuah array yang besar dari word atau byte, yang ukurannya mencapai ratusan, ribuan, atau bahkan jutaan. Setiap word atau byte mempunyai alamat tersendiri. Memori Utama berfungsi sebagai tempat penyimpanan yang akses datanya digunakan oleh CPU atau perangkat I/O. Memori utama termasuk tempat penyimpanan data yang sementara (volatile), artinya data dapat hilang begitu sistem dimatikan.
Sistem operasi bertanggung jawab atas aktivitas-aktivitas yang berkaitan dengan manajemen memori seperti:
• Menjaga track dari memori yang sedang digunakan dan siapa yang menggunakannya.
• Memilih program yang akan di-load ke memori.
• Mengalokasikan dan meng-dealokasikan ruang memori sesuai kebutuhan.
c. Manajemen Berkas
Berkas adalah kumpulan informasi yang berhubungan sesuai dengan tujuan pembuat berkas tersebut. Berkas dapat mempunyai struktur yang bersifat hirarkis (direktori, volume, dll.). Sistem operasi bertanggung-jawab:
• Pembuatan dan penghapusan berkas.
• Pembuatan dan penghapusan direktori.
• Mendukung manipulasi berkas dan direktori.
• Memetakan berkas ke secondary storage.
• Mem-backup berkas ke media penyimpanan yang permanen (non-volatile)
d. Manajemen Sistem I/O
Sering disebut device manager. Menyediakan "device driver" yang umum sehingga operasi I/O dapat seragam (membuka, membaca, menulis, menutup). Contoh: pengguna menggunakan operasi yang sama untuk membaca berkas pada hard-disk, CD-ROM dan floppy disk.
Komponen Sistem Operasi untuk sistem I/O:
Buffer: menampung sementara data dari/ ke perangkat I/O.
Spooling: melakukan penjadualan pemakaian I/O sistem supaya lebih efisien (antrian dsb.).
• Menyediakan driver untuk dapat melakukan operasi "rinci" untuk perangkat keras I/O tertentu.
e. Manajemen Penyimpanan Sekunder
    Data yang disimpan dalam memori utama bersifat sementara dan jumlahnya sangat kecil. Oleh karena itu, untuk meyimpan keseluruhan data dan program komputer dibutuhkan secondary-storage yang bersifat permanen dan mampu menampung banyak data. Contoh dari secondary-storage adalah harddisk, disket, dll. Sistem operasi bertanggung-jawab atas aktivitas-aktivitas yang berkaitan dengan disk-management seperti: free-space management, alokasi penyimpanan, penjadualan disk.
f. Sistem Proteksi
    Proteksi mengacu pada mekanisme untuk mengontrol akses yang dilakukan oleh program, prosesor, atau pengguna ke sistem sumber daya.
Mekanisme proteksi harus:
• membedakan antara penggunaan yang sudah diberi izin dan yang belum.
specify the controls to be imposed.
provide a means of enforcement.
g. Command-Interpreter System

    Sistem Operasi menunggu instruksi dari pengguna (command driven). Program yang membaca instruksi dan mengartikan control statements umumnya.

Referensi : 
vlsm.org, Komponen Sistem Operasi, 
http://bebas.vlsm.org/v06/Kuliah/SistemOperasi/BUKU/SistemOperasi-4.X-1/ch05.html#c20501
Wahyu Wijanarko, Sistem Operasi Terdistribusi, 
http://ilmukomputer.com/2006/08/20/sistem-operasi-terdistribusi/
http://id.wikipedia.org/wiki/Sistem_operasi 

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