Bad Sectors

As all we know that a hard drive is made of the millions of sectors and it is possible that some of these sectors gone bad.As I a want to told you that when a hard drive is manufactured it still contains some bad sectors and as the life span of hard drive's increase or it gets old the number of bad sectors increased in it.A sector is a small area on the surface of the hard drive or a floppy disk.As all we know that each hard drive have several platters.The platters are the disc that are covered with magnetic material which is used to hold data and they are divided into a number of concentric rings known as track.If we talk about a floppy disk(1.44 MB) than it contains only one platter and having about 160 tracks.But in the case of hard drive it contains a lot of tracks and each track is divided into smaller storage areas called sectors.Now when a sector goes bad the whole data that it contains lost and it cannot be recovered.Bad sectors never affects the data of the remaining hard disk and disk is still completely usable.The main problem with the bad sectors is that it cannot be repaired,it only marked as unusable.Once you marked these bad sectors as unusable then operating system will never store data in these areas and storage capacity of your hard drive is decreased.

Avoid Swapping of Files

When Windows loads, it moves certain parts of the operating system to the swap file anyway, regardless of whether it has run out of RAM or not. This is very good for systems with less memory, since it leaves some free RAM and applications will start much faster. Otherwise, when you start an application and memory is required, Windows will have to first move all this data to the swap file to free up RAM. This functionality is usually not required on systems with 256 MB or more RAM, especially if they only run common productivity tools such as Office and Internet applications. You can prevent Windows from using the swap file until absolutely required by adding the line below to the [386Enh] section of the \Windows\ system.ini file.

ConservativeSwapfile Usage=1 You can edit this file in Notepad. In case you face any problems such as programs crashing frequently, remove this line and reboot.

Enable your computer's DMA

Direct Memory Access (DMA) is a technique that hard disks and CD-ROM drives can use to transfer data directly to and from memory, without passing through the processor. DMA reduces the load on the system processor since data transfers do not require monitoring by the CPU. With DMA, a write or read operation can be executed in two to four clock cycles. Without DMA it will cost the CPU a minimum of 16 clock cycles per operation. Not only do disk read/write operations gain a significant boost in speed, but Windows also works faster, since it can load system files much faster and also accesses the swap file at higher speeds. Older hard disks and CD-ROM drives do not support DMA, but almost all computers today use DMA-compliant devices. In case you face a problem after enabling DMA, reboot Windows to Safe Mode and disable the option. Also, DMA needs to be enabled from the BIOS, but again, on most computers, this is on by default. DMA is supported only in Windows 95 OSR 2 and later. To enable DMA, open Control Panel > System > Device Manager.Expand the Disk drives tree, select the hard disk and click Properties. Under the Settings tab, check the DMA option. Repeat this for all other hard disks and the CD-ROM or DVD-ROM drives.

File System Properties

Changing the File System settings can also provide better performance. First, change your computer's role to a Network Server, even if it is not one. Open Control Panel > System > Performance and click File System. Under the Hard Disk tab, change the typical role of the computer to Network server instead of Desktop computer. The setting controls the size of various internal data structures used by the 32-bit file access driver (VFAT). When you use the Desktop computer setting, VFAT allocates memory to record the 32 most recently accessed folders and 677 most recently accessed files, consuming approximately 10 KB of memory. With the Mobile or docking system setting, VFAT allocates memory to record 16 folders and 337 files, taking up around 5 KB of memory. As a Network server, VFAT allocates around 40 KB of memory to record
64 folders and 2,729 files. With the kind of memory available on systems today, this slight overhead hardly makes any difference, especially considering the performance gain it provides.

Optimize your Virtual Memory

The way virtual memory is configured tremendously affects Windows performance. This is true for all versions of Windows, including the now-obsolete Windows 3.1. The swap file is what Windows uses to store temporary data when it runs out of RAM. Thus, your working is not limited by the amount of RAM on your machine. However, for a program to be able to use this data, it must be transferred back to the RAM. The data that is not immediately required is moved to a part of the hard disk and recalled when required. However, since hard disks are nowhere as fast as RAM, swapping data back and forth drastically reduces speed. No matter how much RAM you have, Windows will always use the swap file for some infrequently used parts of the OS (read the next tip to see how to avoid this).

By default, Windows uses a variable swap file that is created on boot up and where the size is dynamically modified when required. Though this works just fine, it is not the most optimal. You can never get the speed of RAM from the hard disk, but you can make it slightly faster. The best way to configure the swap file is to have a permanent swap file, preferably on a dedicated partition. This minimizes the effect of disk fragmentation and increases seek time. Another practice that a few power users have adopted is to place the swap file on the first partition and the operating system on the following partition. Data closer to the center of the drive is read slightly faster than data at the periphery. This is especially useful for PCs with only 64 or 128 MB of RAM where data would frequently be swapped to the hard disk and can be easily done with BIOSes that allow booting from the D drive.

To change the swap file settings, open Control Panel > System > Performance and click Virtual Memory. Choose 'Let me specify my own virtual memory settings' and select the drive for the swap file. Note that no matter what partition you boot from, it will always appear as the C drive from DOS and Windows 98, and the first partition that is recognized as C by the BIOS will be assigned a higher drive letter. Set the minimum and maximum size for the swap file. Both these numbers should be identical to set a permanent (non-variable) swap file. Ideally, it should be two-and-a-half times the amount of RAM on your system, but if you have a separate partition for it, you may not want it to be less than 512 MB-if it is lower, it will have to be a FAT16 partition, not FAT32.

Concept of Thrashing

If the number of frames allocated to a low priority process is lower than the minimum number required by the computer architecture then in this case we must suspend the execution of this low priority process.After this we should page out all of its remaining pages and freeing all of its allocated frames.This provision introduces a swap in,swap-out level of intermediate CPU scheduling.Let take a example of a process that does not have enough number of frames.If the process does not have the number of frames it needs to support pages in active use, it will quickly page fault.The oly option remains here for process is to replace some active pages with the page that requires a frame.However,since all of its pages are in active use,it must replace a page that will be needed again right away.Consequently,it quickly faults again and again that mean replacing pages that it must bring back in immediately.This high paging activity is called Thrashing.Or we can say that a process is Thrashing if it is spending more time in paging then executing.Thrashing results in severe performance problems.

Client Server Communication with the help of Sockets

A socket is defined as an end point for communication between client and server.A socket is identified by a IP address concatenated with the port number.In general all sockets work on the client server architecture.In server client system, server waits for the incoming client request by listening to a specified port.Once the server received the request from the client it accepts the connection from the client socket to complete the connection.As there are some standards ports already defined for some specific services like a telnet server listens to port 23,a ftp server listen to port,a http server listens to port 80.All ports below 1024 are considered well known and we can use them to implement standard devices.Now when a client process requests to initiates a connection with the server,it is assigned a port by the host computer.This port is some arbitrary number greater that 1024.

Let us consider a example,there exists a client on host with IP address 185.145.23.87 wishes to establish a connection with the web server which is listening on the port 80 and having IP address 164.25.17.5,now let host X is assigned a port number 1547.Now this connection will contain a pair of sockets (185.145.23.87:1547) on host X and (164.25.17.5:80) on the web server.Now the packets traveled between the hosts are delivered to the appropriate process based on the destination port number.The main thing that kept in mind during connection that all connections must be unique,that means if another process on host X wants to establish a connection with web server then the port number that is assigned to this process must be greater that 1024 and different from 1547.

Hope you found this post useful.Waiting for your responses for further improvement.
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