1)What is the difference between cloud computing andclient/server computing. Wha
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Question
1)What is the difference between cloud computing andclient/server computing. What types of resources are used on each, what kind of applications, and what type of security is supported by each.
2)Linux has many file systems, one is called a Journaling file system, what are the advantages and disadvantages of this file system, how large can it be, what is the impact on the operating system as far as “house keeping” and are there any security features. Explain when one would use th is file system as a choice over any other offered on a standard Linux distribution.
3)Explain the differences between a Master boot record (MBR), Master File Table (MFT) and Basic Input/output System (BIOS) and a Hardware abstraction layer (HAL). Are there any similarities or overlapping responsibilities ?
4)What are the differences between a virtual desktop, virtual machine and virtual server. In what conditions would you use one of the other? Which has the largest domain (Pervasiveness)?
5)Of the types of Digital Subscriber Lines (DSL), which is the most common?, which is the fastest? which has the longest distance? How do the speeds of DSL compare to a T1 line?
Explanation / Answer
Answer No. 1 -
Client Server Computing : In the great-wide world of computing there are only two kinds of applications,
Standalone simply means the user-interface and the business logic and the datastore and any and all resources are completely self contained within a single execution environment - the end-user's machine.
In contrast, client-server means there is some logical segregation of these components, services, and resources. Typically we see user-interfaces in a local execution [aka "client"] and business and data store and other resources in a remote execution [aka "server"]. Some examples,
Cloud Computing : Cloud computing is an abstraction of traditional server hosting solutions. Instead of buying 10 servers myself to run and manage in my own operations datacentre, I now lease X servers from a vendor where X is a variable number decided by me whenever I want.
There is a distinct advantage to leveraging a cloud. If I bought 10 servers, I must manage and maintain these 10 servers even if they are underutilized [say only 1 server is used 90% of the time, while all 10 are pinned 10% of the time at peak hours]. That means I am paying way too much in maintenance for 90% of the time, while being inflexible when I need to grow the remaining 10%.
The advantage of cloud computing is that "someone else" is managing the server farm for us, and is willing to lease out a variable number of machines to us on demand. So in our scenario above, I could lease 1 machine for 90% of the time in off-hours, and scale up to 10 or more machines the remaining 10% of the time.
Microsoft takes this abstraction one step further with Windows Azure. They do not lease generalized servers, but application domains. This is the one example [to mind] where a cloud implementation has actual design implications - but it is predicated on the same premise of elastic hosting.
Answer No. 2:
Journaling File System : A journaling FileSystem is a hybrid between a traditional filesystem and a LoggingFileSystem. Writes to the filesystem are moved to a log first and then later moved to the traditional component.
Advatage of Journaling File System : 1) Faster system restart time after a crash because the computer does not have to examine each filesystem in its entirety to guarantee its consistency. Journaling filesystems can be made consistent by simply replaying outstanding, complete entries in the log. Incomplete entries in the log are simply discarded when the log is replayed.
2) Greater flexibility. Journaling filesystems often create and allocate inodes as they are needed, rather than preallocating a specific number of inodes when the filesystem is created. This removes limitations on the number of files and directories that can be created on that partition.
3) Faster file and directory access. All the journaling filesystems discussed in this book use more sophisticated algorithms for storing and accessing files and directories than do traditional non-journaling filesystems. The JFS, ReiserFS, and XFS journaling filesystems all use advanced data structures such as B-Trees, B+Trees, or B*Trees to speed up looking up and storing inodes.
4) Writing to the log can be optimized. Like all filesystem updates made by non-journaling filesystems, writes to the log used by a journaling filesystem must be made synchronously. However, the logs used by journaling filesystems typically can be written to more quickly than a filesystem itself for two main reasons: they can be written to in raw fashion rather than having to go through the filesystem, and log writes almost always consist of appending data rather than inserting it. Most logs are preallocated, fixed-size, circular, and use custom read and write routines.
Disadvantage Of Journaling File System :
1) Budgetary or irrational design restraints can give a wrong expectation of resilience and cause designers to be complacent about Disaster Recovery backups.
2) Defragmentation : There is no online ext3 defragmentation tool that works on the filesystem level.
3) Undelete : ext3 does not support the recovery of deleted files. The ext3 driver actively deletes files by wiping file inodes for crash safety reasons.
Answer No. 3
MBR : MBR stands for Master Boot Record. In MBR, first in hard disk, it identifies how and where an Operating System is located, so that it can be loaded or booted into the computer’s main memory area. It is also used for starting or partitioning the information in computer drive.
MFT : MFT stands for Master File Table. It any information or structure is damaged, the partition will be inaccessible. MFT cannot be repaired. If damaged file or structure exists, then file oriented recovery will be used.
BIOS : BIOS (basic input/output system) is the program a personal computer's microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer's operating system and attached devices such as the hard disk, video adapter, keyboard, mouse and printer.BIOS is an integral part of your computer and comes with it when you bring it home. (In contrast, the operating system can either be pre-installed by the manufacturer or vendor or installed by the user.) BIOS is a program that is made accessible to the microprocessor on an erasable programmable read-only memory (EPROM) chip. When you turn on your computer, the microprocessor passes control to the BIOS program, which is always located at the same place on EPROM.
When BIOS boots up (starts up) your computer, it first determines whether all of the attachments are in place and operational and then it loads the operating system (or key parts of it) into your computer's random access memory (RAM) from your hard disk or diskette drive.
HAL : Hardware abstraction layer (HAL). A hardware abstraction layer (HAL) is a logical division of code that serves as an abstraction layer between a computer's physical hardware and its software. It provides a device driver interface allowing a program to communicate with the hardware.
The main purpose of a HAL is to conceal different hardware architectures from the OS by providing a uniform interface to the system peripherals.
Answer No. 4
Virtual Desktop : Desktop virtualization software separates the physical machine from the software and presents an isolated operating system for users. Desktop virtualization tools include Microsoft Virtual PC, VMware Workstation and Parallels Desktop for Mac.
The benefits of desktop virtualization include:
1) Cost savings because resources can be shared and allocated on an as-needed basis.
2)More efficient use of resources and energy.
3)Improved data integrity because backup is centralized.
4) Centralized administration.
5) Fewer compatibility issues.
Virtual Machine A virtual machine (VM) is an operating system (OS) or application environment that is installed on software, which imitates dedicated hardware. The end user has the same experience on a virtual machine as they would have on dedicated hardware.Specialized software, called a hypervisor, emulates the PC client or server's CPU, memory, hard disk, network and other hardware resources completely, enabling virtual machines to share the resources. The hypervisor can emulate multiple virtual hardware platforms that are isolated from each other, allowing virtual machines to run Linux and Windows Server operating systems on the same underlying physical host. Virtualization limits costs by reducing the need for physical hardware systems. Virtual machines more efficiently use hardware, which lowers the quantities of hardware and associated maintenance costs, and reduces power and cooling demand.
Virtual Server On the Internet, a virtual server is a server (computer and various server programs) at someone else's location that is shared by multiple Web site owners so that each owner can use and administer it as though they had complete control of the server. Some Internet service providers (ISPs) offer a virtual server service instead of, or in addition to, virtual hosting. Using a virtual server, a company or individual with a Web site can not only have their own domain name and IP address, but can administer their own file directories, add e-mail accounts and address assignments, assign multiple domain names that resolve to a basic domain name without involvement from the ISP, manage their own logs and statistics analysis, and maintain passwords. Users of a virtual server, however, do not have to manage the hardware aspects of running a server and effectively share the cost of expensive line connections to the Internet.
Anser No. 5
DSL is a generic term used for a family of related technologies, including RADSL, ADSL, SDSL, IDSL, and others. The leading DSL technologies being deployed today include:
1) RADSL - (Rate Adaptive Digital Subscriber Line)
2) ADSL - Asymmetrical Digital Subscriber Line : ADSL supports a range of asymmetric (higher downstream than upstream) data speeds that can reach up to 7 mbps downstream and 1.5 mbps upstream. ADSL can deliver simultaneous high-speed data and telephone service over the same line.
3) ADSL Lite (or G.lite) : This is a lower speed version of ADSL and provides downstream speeds of up to 1Mbps and upstream speeds of 512 kbps, at a distance of 18,000 feet from the service provider’s premises. It is intended to simplify DSL installation at the user’s end.
4) R-ADSL - Rate-Adapative Digital Subscriber Line : The R-ADSL provides the same transmission rates as ADSL, but an R-ADSL modem can dynamically adjust the speed of the connection depending on the length and quality of the line.
5) HDSL - Hight Bit-Rate Digital Subscriber Line: The HDSL provides a symmetric connection, that is, upstream speeds and downstream speeds are the same, and range from 1.544 Mbps to 2.048 Mbps at a distance of 12,000–15,000 feet. Symmetric connections are more useful in applications like videoconferencing, where data sent upstream is as heavy as data sent downstream. HDSL-II, which will provide the same transmission rates but over a single copper-pair wire, is also round the block.
6) IDSL - ISDN Digital Subscriber Line : The ISDN Digital Subscriber Line provides up to 144 kbps transmission speeds at a distance of 18,000 feet (can be extended), and uses the same techniques to transfer data as ISDN lines. The advantage is that, unlike ISDN, this is an ‘always on’ connection.
7) SDSL - Symmetric Digital Subscriber Line : SDSL supports symmetric (equal downstream and upstream) data transmissions up to 1.54 mbps.
8) VDSL - Very High Bit-rate Digital Subscriber Line : VDSL is the fastest of all xDSL flavors and provides transmission rates of 13–52 Mbps downstream and 1.5–2.3 Mbps upstream over a single copper-pair wire, at a distance of 1,000–4,500 feet from the service provider’s premises.
Comparison factor between DSL and T1 line : T1 connection can be compared with DSL over a matrix of factors listed below.
Speed: The speed of T1 is somewhere between 384 k and 1.5 mb whereas the speed of DSL is somewhere between of 128k and 2.0 megabit. This is the most important point you need to keep in your mind while T1 speed comparison vs. DSL speed.
Government regulation: In the case of T1 line there are state and FCC regulations mandate. The quality level is defined. The customer care service has to be responsive. On the other hand, DSL connection is unregulated. There are no state and FCC regulations in place. Circuit cost escalations, defined quality level and customer service responsiveness are at the discretion of local bell and the third party DSL provider.
Service level Guarantee: In T1 line there is 100 per cent connection uptime and 85 ms round trip package whereas in DSL there are no such facilities.
Speed versus distance: For T1 line there is guaranteed fixed speed independent of distance. On the other hand, for DSL connection speed is dependent on distance from Telco central office. The further away your place the slower the speed.
Distance limit: In the case of T1 line there is no limitation as far as the distance from CO is concerned where as in case of DSL connection the distance is limited to 3.5 miles from central office.
Circuit availability: The T1 line service is widely available. But DSL connection service is not available in small towns and villages.
Physical circuit: The T1 line service is developed for digital data service and may be delivered via fiber optics. DSL are made for voice grade copper telephone circuits. Fiber bridges or taps will prohibit DSL.
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