Oracle write up on the way

Oracle write up on the way!!!

How safe is our data in HDD ??

Hello All,

Greetings. Hope you all had a fantastic weekend, It was same for me though, spent sometime in watching some old hollywood movies and here am back with a handful. Welcome once again.

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Let me recollect the points from my last post :-)



We saw about servers,storages who are the leaders in the market.Then we also were seeing our data willl get stored in lot of harddisk drives in a storage.So how our data is protected incase of harddrive failures.So the answer is RAID.


RAID ( Redundant Array of Inexpensive Disks) :

In a very easy term, it is spreading of data in several disks instead of one.For explaining this a elucidation of RAID types is a must.It can implemented using a hardware or using a software.

Harware RAID:
Some of them use a hardware raid controller card to do all the RAID calculations.RAID controllers also come in the form of cards that act like a SCSI controller to the operating system but handle all of the actual drive communications themselves. In these cases, you plug the drives into the RAID controller just like you would a SCSI controller, but then you add them to the RAID controller's configuration, and the operating system never knows the difference.

Software RAID :
Software RAID implements the various RAID levels in the kernel disk (block device) code. It offers the cheapest possible solution, as expensive disk controller cards or hot-swap chassis are not required. Software RAID also works with cheaper IDE disks as well as SCSI disks. With today's fast CPUs, Software RAID performance can excel against Hardware RAID.

Types:
There are several RAID levels such as RAID1(Mirror),RAID 0(Stripe),RAID 5(parity),RAID 6(Distributed Parity) and so on.Let me explain some of this types.


RAID 1 :

Here data is duplicated or mirrored.That is data is mirrored one to one.So minimum we need two drives.Lets take a example with two hard drives.If a write happens say "A"on one harddisk drive it will be written on second drive also.Like this if we use 4 hard drives, we end up in using only 2 as remaining 2 are mirrored.Even if a hard disk fails the data can be recovered from its mirror.When a read happens it can read data from any of the drives from mirror.Since RAID-1 requires doubling the number of disk drives to store the data, people tend to think of RAID-1 as the most expensive type of RAID.


RAID 0 :

Data is striped on to the harddrives.Its like a paint brush.No mirroring or no redundancy.Only advantage here is its really fast. A RAID 0 array requires a minimum of two drives. A RAID 0 configuration can be applied to a single drive provided that the RAID controller is hardware and not software (i.e. OS-based arrays) and allows for such configuration.As per our classic example of two drives,if one drive fails we will lose data.

RAID 5 :
So RAID 1 is expensive and RAID 0 has no data safety.So how can this be addressed??The answer is RAID 5.
Here data is spreaded across all drives and XOR calculation of data is calculated in a distributed way.So the parity information is on all drives.It requires minimum 3 hard disks.It is inexpensive and safe too.

In my next post i will discuss about what is data center,and the career paths that you all can look into...

Cheers,
SabariGirish

Server and storage Life!!

Storage :

Server :

Well this week i have decided to give a overview of what exactly is a server,storage and what it does.. Its very important to know about this as most of the mid to high end business centers have a huge deployment of this in their datacenters.

Client - Server :

Let me give a short note on client-server model before i explain about server and storage.

Server is a hardware which takes requests from clients (it might be a desktop or another server) and then processes the requests and gives it back to client..Lets take a example to make it clear.

Normally we use irctc site to book a ticket.So our laptops are considered as clients.The request will go and hit the IRCTC's main server which might run some application for booking tickets.

So we fill all our data and it gets stored in their repository called database.The database will reside in another server called database server.The application and database are very close and will interact with each other every time.

Inotherwords application is the frontend what we are seeing and database is the backend what we cant see..!! We use IRCTC's ticket reservation application to book a ticket which runs on a server and the details given by us are stored in a database which resides in another server.

Based on the functionality we call the servers as Application server,database server or if its used for email purposes its called a mail server.

Now let me explain about server.

Servers are usually accessed over a network they may run in headless mode without a monitor or input device.Many servers do not have a graphical user interface (GUI) as it is unnecessary and consumes resources that could be allocated elsewhere. Similarly, audio and USB interfaces may be omitted.
Servers often run for long periods without interruption and availability must often be very high, making hardware reliability and durability extremely important. Although servers can be built from commodity computer parts, mission-critical servers use specialized hardware with low failure rates in order to maximize uptime. For example, servers may incorporate faster, higher-capacity hard drives, larger computer fans and uninterruptible power supplies that ensure the servers continue to function in the event of a power failure. These components offer higher performance and reliability at a correspondingly higher price. Hardware redundancy—installing more than one instance of modules such as power supplies and hard disks arranged so that if one fails another is automatically available—is widely used.

There are so many other vendors like HP,IBM,SUN(Now oracle),DELL who manufactures servers.These servers will be extremely powerful.

Storage :

Ok here let me take a banking example as it is easy to explain on what is a storage..Everybody will have a bank account and we do lot of transactions daily..So there needs to be a safe place were a bank can store all this data.Nowadays nobody is using paper and its all computerized.

So all our data will be stored in a high capacity/performance machine which can store data called a " Storage".

This ranges from GB's to TB's(Terrabyte) to PB's(PetaBytes).

This storages will have high capacity harddisk drives with some processor which tells the storage and how to store/retrieve the data...So when a server sends a data the storage saves it,and when the server requests for a data storage gives the required data..

Major storage vendors in the storage industry are EMC,HITACHI,NETAPP,SUN,IBM,HP & DELL.

When we say about Harddisk the harddrives are more prone to failures.So how are they protected againt failures,where are all this equipments like servers and storage are kept,i will give all this details in my next post...

Cheers.

An introduction!!

Hello All,



Iam giving a try to write a blog which might help the now college going students on what exactly is a hardware industry...This is so different from the regular C,C#,Java,HTML and boring coding stuffs.



We see a lot of people in this coding area.Tonnes and tonnes of people know about coding and development..



The area of hardware is unsullied and so you all should give a try,,



First of all, i request you all to learn a Unix Operating system like RedHat or Sun Solaris.The current industry requirement for the above said O/S is huge..Once you have this,you have to start developing skills on scripting languages like perl or shell scripting..

Nowadays industries hottest ceritifications are from hardware companies like EMC,IBM,CISCO,JUNIPER,SUN,NETAPP etc...

And all these companies play a very important role in our day to day life..Though we are seeing a rough patch in IT sector from last year,the hardware industry still looks pretty healthy..


So now my idea here is to give a good view of so many things about the above mentioned companies,about their hardwares and the hottest thing happening in the current hardware industry.,,



I welcome all of your suggestions on improving this post after reading it..



Cheers,

SabariGirish