IIITD: System Management

Monday, August 2, 2010

VIDEO CONVERTERS

Hello everyone
We all want to have movies or clips on our cell phones but most of us have video clips(in 3 gp) with an awful quality. Imagine hearing some bollywood song in 3gp,it emits a creaking sound here is a solution-
first of all look into your phone's manual and find what are the video formats supported and what is your screen resolution.

if you love to watch clips or songs on your cell log on to www.effectmatrix.com and download total video converter. It is an excellent converter which gives superb video aand audio quality.import files and convert them.You can set the quality screen size etc,if not sure jast select your phone model(if nokia and sony),explore the options.

Movies take a lot of time to convert so you have to compromise with quality,just use freez 3gp converter avaliable on smallvideosoft.com,believe me its the fastest . I have converted a whole dvd by freez in just 38 min 25 seconds !!

Endianness

Before i start with this post, i would like to share with my friends that this my first experience at bloging or any sort of posting on the net, i hope it is worth your precious time....

Endianness deals with integer representation in a computer . Now, we all know that there are certain human languages that are read from left to right like English,Hindi and then there are some languages like Arabic that are read from right to left.Similarly, integers are represented as sequence of bytes with the most significant byte on the left(The Big Endian),in some representations, while in others it is placed on the right(The little Endian).

Now lets see the main advantage of the two systems:-
1)The little Endian system has the property that the same value can be read from the memory at different lengths... Therefore, the value read from 32-bit memory can be read from the same address as either 16-bit memory or 8-bit memory. all of which retain the same numeric value.
2)The big Endian representation helps to obtain an approximation of the multi-byte value by reading the most significant portion instead of the complete representation.

Address Big-Endian representation of 1025 Little-Endian representation of 1025
00 00000000 00000001
01 00000000 00000100
02 00000100 00000000
03 00000001 00000000

For moe info, you can use the following links:-
http://en.wikipedia.org/wiki/Endianness
http://3bc.bertrand-blanc.com/endianness05.pdf

Blu-ray Discs

Blu-ray discs are optical storage media and look similar to regular CD/DVDs (they are all of the same size). But they can store 10 times the data in a single DVD.

NA = nsinθ ; n = refractive index. Since θ1>θ2, NA(BD) > NA(DVD)

The name "Blu-ray" comes from the blue laser being used to read and write. There are GaN (Gallium Nitride) diodes that produce photons of 405nm directly. 400nm is the wavelength of the violet component of the visible spectrum so the "blue laser" actually appears violet to the human eye. By decreasing the wavelength from 650 and 780nm used for DVDs and CDs respectively, and increasing the aperture from 0.60 to 0.85, the laser can be focused to a smaller area. Hence, more data can be stored in the same amount of space.

In BDs, the distance between the surface of the disk and the surface upon which the data is actually recorded is 0.1mm. This is 1/6 times the distance for a regular DVD. Since the discs are made of plastic, the incident angles can change a little due to disc warping. To check this problem, the NA is increased (to an extent) and the cover layer's thickness is decreased.

Cover layer thickness is reduced to check distortion of the laser spot.

Typical BDs can store 25GB if they are single layered, and 50GB if they are double layered.
"Double-layered" refers to the presence of two recording layers inside the protective cover layer. Each recording layer can store 25GB of data. Pioneer Corp. recently developed a BD with 20 recording layers which allows it to store 500GB of information inside a single BD!

Structure of single-side, double-layer BD

And finally, regarding the popularity of BDs, they are mostly used to store HD videos since the regular DVDs can only store Standard Definition (SD) videos. When HDTVs become widespread, BDs are expected to replace DVDs. For the time being, companies such as Sony, Panasonic, Phillips, Samsung, Pioneer and LG have developed BD drives that are compatible with BDs and DVDs both. This is known as Backward Compatibility and is a measure to ensure that once newer media like BDs become popular, the older storage media do not become obsolete.

Photographs courtesy : http://panasonic.net/blu-ray/technology/

Sunday, August 1, 2010

RAID

RAID stands for Redundant Array of Inexpensive/Independent Disks.

RAID allows a user to store data in multiple places at a time(redundancy) in a balanced way so as to improve performance and data retrieval. It stores the data on multiple hard disks and then combines them into a high performance logical unit where all the drives in the unit are interdependent thus improving Input/Output performance. To put it in simple words, data is spread over different disks but to the operating system and the user, it would appear as if the data is present in one disk only.

An example of improved performance: One set of data is being written to one disk and at the same time another set of data is being retrieved from another hard disk thus speeding up the input/output process.

Thus with RAID we can have:

1) Higher data transfer rate on large data accesses

2) Higher Input/Output rates on small data accesses

Now the question arises "How is the data written to the disks?"

There are several ways of doing this but I shall discuss only 2 of them: Block-level Striping and Mirroring.

Block-level Striping(Raid 0)

In this case, chunks of data is written to different disks. Each disk's storage space is partitioned into "units ranging from a sector(512 bytes) up to several megabytes" (taken from http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci214332,00.html)

Supposing we have a data consisting of 6 parts(D1,D2,D3,D4,D5 and D6). Parts D1,D3 and D5 will be stored in disk 1 whereas D2,D4 and D6 will be stored disk 2(they could be stored in more than 2 disks also, but I'm just giving an example here).

Advantage of this method: smaller chunks of data can be read from the drives thus increasing bandwidth as more data can be read at a time.

Disadvantage: if one disk fails, then the entire data is inaccessible.

Mirroring(Raid 1)

In this case, the same data is duplicated 100% to 2 or more disks thus showing the "mirroring" aspect.

Advantage of this method: Even if one disk fails, we can still read the whole data from the other disk where the data was stored, provided it is working fine. Thus our system can still stay up and running while the affected disk is being replaced!

Those who want to know more about the other ways of doing this, check this link out

http://en.wikipedia.org/wiki/RAID#Standard_levels

Now we come to the advantages and disadvantages of using a RAID disk

Advantage:

1) They can make excellent backup drives especially when they are employed as backup devices to the main drives and particularly when they are located away from the main system.

2) It increases the performance and reliability of a system as regular checks are done to check for any possibility of a system crash

Disadvantage:

1) RAID disks are essentially designed and extensively written for servers. Thus if there is a server, there has to be a network as well and this can cause configuration issues as each network is different.

2) High cost of Purchase (doesn't cost less than a few thousand of dollars)

This post would be incomplete without any mention of WHEN do we use a RAID. It is all very well knowing what RAID does but not knowing when to apply it can be problematic in view of the high cost of purchase as mentioned above.

We can use them in mainly 3 ways:

1) Business Servers: Large business companies require a secure way of storing large amounts data without suffering any loss of the same. RAID can be used for this purpose especially if it is stored in a remote location where accidental erasure of data is pretty much impossible to do.

2) Workstations: "Individuals who are doing intensive work such as video file editing, graphical design,etc. should use a RAID" (taken from http://www.pcguide.com/ref/hdd/perf/raid/why.htm) RAID 0 will provide the improved performance needed in many of these applications (remember what I wrote earlier about improved bandwidth?).

3) Home PC: Most of us use this and we don't need RAID as the high cost of purchase is not justified by the activities we perform with the PC. It's better for us to use SATA/IDE instead (For those who don't know what SATA/IDE is, go here http://smblog.iiitd.com/2010/07/hard-disks-advantage-of-sata-over-ide.html).

Thus we can say that RAID is best used by big companies that can afford to purchase it as it gives them their money's worth over the security of their data which is a very important thing in this world.

If anyone wishes to add something else to the above, go ahead and do so =D

SOURCES:

http://en.wikipedia.org/wiki/RAID

http://www.webopedia.com/TERM/R/raid.html

http://www.ecs.umass.edu/ece/koren/architecture/Raid/raidhome.html

http://www.raid-data-recovery.net/advantages-raid.html

IMAGES:

http://en.wikipedia.org/wiki/RAID#Standard_levels

Friday, July 30, 2010

CPU-Z V/S DMIDECODE..and..HOW TO USE THEM?

I wouldn't actually call it a post being posted here because amarjeet sir wanted it to be here on the blog..After all those discussions on the first post of this blog over how to get the details of your processor,ram,OS..etc just on the click of a button....and then later over utilities like CPU-Z and DMIDECODE..this had to be there..either as my personal assignment or some question in the class or as it was destined to be..As a post..titled--CPU-Z V/S DMIDECODE..What are these actually??how do I install them and use them??...I hope I end up clearing all your doubts..

OVERVIEW:
Each computer is like a specific human being.. having a processor,ram,hard-disk,motherboard different from others in one or more ways...and getting into the details the complexity of each component increases..some of these computers might have pentium-4,some may have a dual core..the ram might vary from an obsolete SD-Ram to DDR1,2 and 3 Rams..the question is..I have all these locked under my laptop or in my cpu..how do I know what are the details of such components in the machine that I am using without any prior knowledge..

There are several ways to get to know that..however..the most user friendly ones are..

If you are working on a windows platform,you could just go to control panel/system...or a shortcut whould be right-clicking your MY COMPUTER icon and selecting properties and then device manager for details about each component, and driver details..

However,some OSs or some specific OS service packages do not provide the necessary information like the Ram type,or may be the the frequency of the Ram..(That's why some of you just couldn't get these details and commented for solutions on the post.

This one is a kind of a universal method..which includes getting the data through the SMBIOS or System Management Basic Input/output System which is actually a special software that interfaces the major hardware components of our computer with the operating system.It is usually stored on the Flash memory chip on the motherboard, but sometimes the chip is another type of ROM.

img links: http://www.washington.edu/lst/help/computing_fundamentals/troubleshootingxp/img/bios.gif
http://www.computerhope.com/help/bios4.gif

You can enter the BIOS by just pressing del or F-11,or F-12 key(depending on ur BIOS version and make) while starting up the computer before the OS boots..

However,Some BIOS interfaces from Pheonix and other firms..in some versions..do not provide the necessary,just like mine didn't.It may provide u with more than what the OS provides..but it's still not everything..

Now,the most important part of this post..if none of the above work,this is your key my friends..For Windows' users...this is a must have..It can provide you with information and details that Windows or even BIOS do not provide..It's actually a UTILITY(A program that performs a specific task related to the management of computer functions, resources, or files, as password...{{source answers.com}) that helps you get all the details about the following:

CPU
Name and number.
Core stepping and process.
Package.
Core voltage.
Internal and external clocks, clock multiplier.
Supported instruction sets.
Cache information. Mainboard
Vendor, model and revision.
BIOS model and date.
Chipset (northbridge and southbridge) and sensor.
Graphic interface. Memory
Frequency and timings.
Module(s) specification using SPD (Serial Presence Detect) : vendor, serial number, timings table. System
Windows and DirectX version
Source : cpuid.com

How to install this thing?? Just as simple as it can be..Download the software from http://www.cpuid.com/ for free..and just run the executable file..You'll be done.(Please don't try to validate your copy,keeping it unvalidated would do.)

Once installed,the software is user friendly to handle.Requires no input.The screen may look like as below

img source: cpuid.com

Now is the most important part...

HOW DOES THIS WORK?? AND CPU-Z V/S DMIDECODE(Linux)

To get information about a device, whatever it is (CPU, GPU, HDD ...) you have two methods:

1- Hardware level access (aka direct or raw access) or,

2- software level access: drivers, or Windows API.

Method 1 is the most accurate, provides the most precise details, but it is dangerous and requires constant updates. Method 2 is safer, less accurate and easier. CPU-Z uses method 1 for CPU information.

About why is method -1 risky?..I had to work out a simple answer.So it's about the Windows kernel system which is organised in so called rings.Ring 0 being the core of kernal..CPU-Z runs in Ring 0 to get the detailed information digged out.But all other applications we use,run in Ring 3,so if there is any error..Ring N-1(i.e. Ring 2 here.) handles the error.But if unfortunately there is an error in Ring-0.All you get is a blue screen being displayed.(However guys,you get to run CPU-Z in Ring 0 only if you are the administrator of your system.If not,it will follow method-2 and run in Ring -3,thus providing less or incorrect information)

Help from: (http://www.techpowerup.com/reviews/Interviews/Franck_Delattre/2.html)

Now,There are also other similar utilities you can try out,close to how CPU-Z works.

One of them is called SPECCY(Thanks to my buddy Apoorv Narang,Ist year, for this information)

Here's the link if anyone needs to try it out http://www.piriform.com/speccy

This is more user friendly,gives enough information about your graphics card too.....

BUT What is DMIDECODE??

First of all,this command is only for use in LINUX. DMIDECODE is actually DMI table decoder.dmidecode is a tool for dumping a computer's DMI (some say SMBIOS ) table contents in a human-readable format. This table contains a description of the system's hardware components, as well as other useful pieces of information such as serial numbers and BIOS revision. Thanks to this table, you can retrieve this information without having to probe for the actual hardware. While this is a good point in terms of report speed and safeness, this also makes the presented information possibly unreliable. The DMI table doesn't only describe what the system is currently made of, it also can report the possible evolutions (such as the fastest supported CPU or the maximal amount of memory supported).
SMBIOS stands for System Management BIOS , while DMI stands for Desktop Management Interface. Both standards are tightly related and developed by the DMTF (Desktop Management Task Force).
As you run it, dmidecode will try to locate the DMI table.You may also use DMIDECODE -t for information not specific to BIOS.If it succeeds, it will then parse this table and display a list of records like this one:

source:http://linux.die.net/man/8/dmidecode

img src:http://www.addictivetips.com/wp-content/uploads/2009/12/BIOSINfo_thumb.png

CPU-Z V/s DMIDECODE

Well,DMIDECODE can't actually be called a counterpart of CPU-Z on LINUX.There are various reasons:

CPU-Z is for Windows,DMIDECODE for Linux.
The CPU-Z is an External utility downloaded from the web.But dmidecode is a command,used in the Linux terminal window.
So,the Dmidecode tool may be called an internal utility of the Linux.
The tables appearing after running DMIDECODE are not that specific,niether do they contain all the necessary details
CPU-Z is much more userfriendly as a software,compared to running commands in Linux.
CPU-Z is highly detailed as it works in Ring 0 of window's kernal system,DMIDECODE itself doesn't get u all the needed,but some modifications in the command(available on google) can help u get almost everything.

For the lucky ones like AMARJEET SIR,who fortunately use MAC..its a piece of cake..just go to about-Mac..and you are done...(APPLE ROCKS)

Do let me know if this was helpful,I know this was long, but I just couldn't help it.

Comments and Questions are invited from all of you.If any one of you tries any of the above specified softwares,please share your experience with us.

If you need me to post anything you want to know about.Feel free to mail me at

arjun10021@iiitd.ac.in

Thanks
Arjun Ahuja

Hard drives getting S.M.A.R.T.

Hard drives have to operate at thousands of rpm , work all day long and maintain a distance of the order of microns between the head and the platter (as we got to know in the lab). So, it is natural the hard drives “die”,i.e., they stop working eventually, resulting in the loss of our data and problems for us.But the S.M.A.R.T. supported drives may just tell you before its going to die, to save us the heartburn.

I stumbled upon this term when we had to collect information about our processors,hard drives and system memory. So I tried to find a little more about this lifesaving technology.So here's what i found....

S.M.A.R.T. stands for Self-Monitoring, Analysis and Reporting Technology and it tries to anticipate hard drive failure by keeping an eye on many of the drive’s crucial properties.

S.M.A.R.T. support is built into most ATA and SCSI hard drives these days. If a hard drive has S.M.A.R.T. support , then it keeps monitoring itself for signs which may lead to a drive failure and warns the user/administrator so that he/she may be able to copy the data to another location before the drive dies.

The first drive monitoring system was introduced by IBM in 1992. Another variant was created by computer manufacturer Compaq and disk drive manufacturers Seagate, Quantum, and Conner which was named IntelliSafe. Compaq submitted their implementation to Small Form Committee for standardization in early 1995. It was supported by various other companies including IBM and was chosen by the committee as the standard due to its flexibility and was named S.M.A.R.T.. According to PCtechguide’s page on S.M.A.R.T. , the smart technology has evolved from just monitoring hard drive activity for data retrieved by operating system to testing all data and sectors of a drive using “off-line data collection”(when drive is inactive).

A Little Info

The most basic information provided by the SMART system is the SMART status. It has two values , “threshold exceeded” or “threshold not exceeded”,which correspond to “drive about to fail” or “drive okay”.A “threshold exceeded” value suggests that the drive is about to fail,i.e., it will not be able to work according to its specifications anymore.

For more information on a drive’s health, SMART attributes can be examined. there are various types of SMART attributes like read error rate,throughput performance,spin up time etc. which have different threshold values defined by the manufacturer and tend to vary from one manufacturer to another. If a attributes threshold is crossed , it may report an impending drive failure, but it all depends on the implementation of SMART attributes by the manufacturer as these attributes were not included in the standard. A list of all the SMART attributes and meanings of their raw values is available at http://en.wikipedia.org/wiki/S.M.A.R.T.

Furthermore, some drives also support various self tests and maintenance tests as a part of SMART system to reduce the chances of sudden disk failure.

-offline

-short

-long

-conveyance

In linux, one can view the SMART properties using the disk utility or by using smartmontools' smartctl utility. A detailed article on how to use this utility and more about SMART is available at http://www.linuxjournal.com/magazine/monitoring-hard-disks-smart (i havn’t tried it yet, if anybody tries it ,let me know about the results).

disk utility screenshots

links and resources:

http://www.pctechguide.com/31HardDisk_SMART.htm

http://www.linuxjournal.com/magazine/monitoring-hard-disks-smart

http://en.wikipedia.org/wiki/S.M.A.R.T.

Thursday, July 29, 2010

PCI, PCI-X, PCI Express - Comparison

A brief intro on Buses and Peripherals

Buses look like "a bundle of wires" or PCB's that terminate at multiple connectors where devices can be plugged in. They are used basically to connect electric components.

Early computer buses were just bundles of wire connecting memory with peripherals(External devices/Hardware which need the host perform a function eg: Mouse, Keyboard.)

The S-100 bus "Card Cage" - The S-100 bus was used in the earliest "Microcomputers"

Technology evolved, computers became sophisticated, and so did these guys.

What we use today:

PCI (Peripheral Component Interconnect)

PCI is a widely used computer bus which acts as a standard interface for connecting peripherals to the computer, in two ways - An integrated circuit embedded in the motherboard, or an expansion card which fits into it's slot.

PCI is capable of allowing high speed of data transfer, which modern peripherals(eg: Graphic cards, Ethernet)require.

More info in PCI found here: http://computer.howstuffworks.com/pci.htm

PCI-X

PCI-X(64 bit) is the 32 bit PCI bus optimized for higher performance. It is twice the width of the PCI and narrower. It runs at higher frequencies, and can manage four times the clock speed. It was developed(by IBM, Microsoft, HP) to increase the performance of high level peripherals like high-end graphic cards and Storage devices, gigabit - speed ethernet, which isn't feasible by the conventional PCI design.

Except for a few changes, The basic structure of PCI and PCI-X are similar, they follow the same protocol and perform the same functions.

PCI Express/PCIE

PCI Express is an innovative new design that is used as an Expansion Card(It can't be connected to PCI/PCI-X directly) to replace PCI and PCI-X.

PCIE operates more like a network than a bus.

In a PCI/PCI-X, one bus handles data from multiple sources at once.

In PCIE, a switch controls several point to point serial connections, these connections are conveyed directly to the device where the data needs to go making a serial interconnect along a switched bus, dedicated exclusively to that slot. Meaning - The PCIE point to point connection connects only two devices at one time.

Each PCIE slot is attached to the motherboard using a unique "lane", which does not share the data path with other PCIE Slots. Multiplying individual data "lanes" to produce interconnects which deliver upto 16 times the bandwidth of a single lane.(This is the reason their slots are referred to as PCI Express*4/PciExpress*16)

Further information on how PCI Express works:http://computer.howstuffworks.com/pci-express.htm

PCIE vs PCI-X - Why PCIE is Superior

Parallel connections (used by PCI-X) undergo problems during high speed data transfer - like electromagnetic interference.

Interconnecting lanes of PCIE give it a higher bandwidth.

Less steps needed to process instructions, due to it's architecture.

Add more.