Tutorial 4 : Introduction to RAID

The world of 56k internet connections, 256MB of ram, 10GB hard drive, and floppy disk has died. The technology driven environment we live in today is always looking for the a way to out due our current solution.  Now a day ram can be bought in multiple gigabytes, and hard drives have reached terabyte level.  Throughout this blog post I will give a basic introduction for various different ways to save your data by using one of the RAID (Redundant Array of Inexpensive Disks).

RAID is storing your information in multiple disk drives but they are treated as one by the computer.  By spreading out the stored information, you will capacity, speed, and reliability in different ways.  In my post I will briefly give an introduction and describe the four most common RAIDs, RAID 1, RAID 0, RAID 5, & RAID 6.

RAID 1 - Mirroring

RAID 1 uses two disk drives and creates two identical copy the data, hence the name mirroring.  Everything that the computer stores RAID 1 will send the information to both hard drive A and hard drive B.  Consequently if for some reason one hard drive A fails, hard drive B will still have all your information safe.  Not only will your information still be safe but your computer does not slow down if a hard drive fails it will continue to run at full speed.  Even though you as the user will probably not notice the difference if a hard drive fails, it is important to have a hot spare disk.  After replacing the dead hard drive A with the hot spare, hard drive B will mirror all the information it has to hot spare and it will be back to normal.  The only con is that RAID 1 is pricey.

Attached diagram demonstrates how the Raid 0 distributes file 1, 2, & 3.  

RAID 0 - Striping
Raid 0 is used with two or more disk.  The more disk that are in use the faster it will run.  What RAID 0 does it distributes the data evenly between the disks in use, that it is why RAID 0 is also known as Striping.  By spreading out the information through different hard drives you gain a lot of speed.  This is ideal for simultaneously working on both read and write request.  Sadly all is not good, thou being the fastest it is also the least dependable.  If one hard drive fails the entire system will fail, crash, and all data will be lost.  It is known that RAID 0 is actually least dependable then just having a stock normal one hard drive you get from a thick client.

Attached diagram displays how RAID 0 spreads out its stored information

RAID 5
Raid 5 uses three or more hard drives and RAID 5 hardware to store information.  Information is stored in all disk excluding one.  For example lets say you are have three hard drives A, B, & C.  Hard drive A & B will be used to store information, while hard drive C will be doing something called parity.  Parity calculates and then stores information on the remaining unused drive.  But don't get int confused there is no certain parity drive.  For example same scenario we have the same three hard drives but now we want to store a new file.  Now hard drive A & C will be in use to store information, while hard drive B is calculating the parity.  By doing this your performance increase drastically, information is read faster, and write speed is common.  If a hard drive fails with RAID 5  no data will be lost.  The system will still be up and running, but unlike mirroring you will loose performance.  With RAID 5 you can substitute a dead disk with the hot spare that I discussed earlier.  After the process of reconstruction the data on the new disk performance will be back to normal.  RAID 5 is commonly found in network servers everywhere.

Attached diagram displays how RAID 5 creates its parity code to save data

RAID 6
RAID 6 extends RAID 5 by adding an additional parity block.  So if you have four disk drives in use when it comes to storing information only two will actually store information, while the other two are calculating the parity.  The reason why this is used is because it protects against read failures during rebuild of a large hard disk which will usually result in loss of massive amount of data.  Performance wise it runs like RAID 5 it reads fast but writes slow and also needs hard ware to support it.

(There is no diagram for RAID 6, due to the similarities that it has with RAID 5)


Just like everything else when it comes to choosing which RAID is right for you, you must due an analysis and see what your trying to get out of the RAID.  For the normal PC user I strongly recommend for you to USE RAID 1.




REFERENCES:
http://en.wikipedia.org/wiki/Raid_0#RAID_0
http://www.ehow.com/facts_5148033_computer-raid.html
All photos have been made in Microsoft Paint, and created by Dario Gonzalez II

Tutorial Blog 3: Different type of internet connections

We live in a very fast pace environment now a days in which we depend more and more on technology.  It has come to the point where virtually anything  from going to classes, paying bills, watching movies, and even keeping in touch with family and friends can be done online.  In my blog I am going to explain the different types of home (there are other types of business connections such as T1 & T3 but those are usually for businesses so I will not be discussing them) internet connections, and  their pros and cons to see which one can benefit you the most. 

1. Analog
In an Analog connection (AKA Dial up) the computer is connected to a modem that dials a phone number which is provided by your ISP (Internet service provider) in order to access the internet.  It is called an analog connection because you access the internet over a dial up signal.

Pros: Very Cheap, Can be used by multiple computers

Cons: SLOW (56k connection), pretty much obsolete in today's age, ties up the phone line, and internet can drop frequently.

Diagram on how an analog connection works

2. Digital Subscriber Line
Digital subscriber line aka DSL is the leading alternative to a analog connection.  Like an analog connection DSL uses a telephone line (2 wire copper telephone line) to connect to the internet but you do not have to use a modem to connect because it is always on and it does not tie up the phone line. 


Pros:  Always on, faster than analog, and does not tie up phone line
Cons: DSL connections work better when you are closer to your server provider.  If you live far away from your server provider you will not be getting what you pay for in terms of internet speed.  Also, you get a decent download rate, but your upload rate lacks severely.  Finally, DSL is not offered everywhere. They are only offered by your location if you live in the country. It is likely to say that DSL will not be provided to you.

Diagram on how DSL works

3. Cable
Accessing the internet through a broadband connection can be done by use of a cable modem.Cable internet connection is a step above a DSL connection.  Like DSL, it is always on but instead of using a telephone line to connect to the interent it uses a TV line.  Cable Internet works by using TV channel space for data transmission with certain channels used for downstream transmission, and other channels for upstream transmission.  The way it works is that you will use a co axle cable to connect the cable modem to the cable input in your wall.  You can either connect your desktop to the cable modem or buy a router to enable wireless internet that will allow you to connect multiple devices to the internet connection.  I personally use a cable connection and I love it.


Pros:  Faster than DSL and Dialup, Does not tie up the phone line, Support heavy data movement such as streaming movies or online gaming, and it is always on.


Cons: Slow connection through online peak hours, initial connection fees can be high, like DSL cable is not available in all areas

 

 

 

 

 

 

 

Diagram on how Cable connection works

4. Wireless Internet
Wireless internet is one of the newest internet connections that have been introduced to the market.  Instead of using a telephone line or TV line to connect to the internet, wireless connections connect through radio frequency band.  This is still fairly new technology and difficult to find a provider for it.


Pros:  Completely wireless, always on, does not tie up the phone line, can be used by multiple devices
Cons: Hard to find a service provider, new technology, and expensive


(no diagram for this type of connection)




I hope my blog helped you in your process in choosing which type of internet connection to choose.


References


http://www.webopedia.com/quick_ref/internet_connection_types.asp
http://www.computertroublesolver.com/
http://www.superpages.com/supertips/cable-internet.html
http://www.wikipedia.org

(Picture made in paint by Dario Gonzalez, excluding cable connection which is found on computertroublesovler.com)