AWS FAQ - Servers and troubleshooting

Q.) Difference between application servers and web servers

Web, application, database server can all run on the same machine or can be distributed across physical machines.



Web server
Server on which your website is hosted. The server will have installed web servers such as apache, IIS.
Deals with HTTP(S) requests. They implement the HTTP specification and know how to handle HTTP request and response object/headers.



Application Server
Server on which your created application which are utilizing your database, web services, etc.
Can also support HTTP requests, but also other protocols, such as RMI/RPC


Other capabilities like load-balancing, clustering, session-failover, connection pooling etc. that used to be in the realm of application servers, are becoming available on web servers as well directly or through some third party products.


Q.) Things to check if your computer is running slow?

1. Too many startup programs

2.Your hard drive is full or nearing an end 
No temp space left.

3. browser has too many add ons

4. Running too many programs at once

5. Your antivirus program could be running scans in the background too frequently

6.Disk Defragmentation
Defragmenting disk minimizes head travel, which reduces the time it takes to read files from and write to the disk.



Q.) Blue screen causes?
Fatal system error
A state where the OS can no longer operate safely
Usually hardware or driver related
Use system restore
Rollback/uninstall device driver
Check that there is enough free space left on the drive where windows is installed
Scan your system for virus
Return BIOS and Hardware Settings to default
Hardware that is not fit properly can also cause sudden death

Q.) Device Manager
Find all your hardware information in one place.
Extention of MS Mgmt Console, that provides a central and organized view of all the MS windows recognized hardware installed in the computer. Like HDD, Keyboard, USB Drive.

It can be used for: 
changing hardware configuration
managing drivers
disabling and enabling hardware

It is like a master list of hardware that windows understand
It is the place where you go if the device is not working correctly.
Such as update a driver, disable the device.
Yellow exclamation point is when windows finds problem with the device.
If a device is disabled it will show red cross or black
It also has error codes if it is having conflict with the system resource

Q.) Virtual Memory
Shortage of RAM is compensated by space in hard disk drive
memory can run out if multiple programs run simultaneously
OS divides the memory into page files or swap files, that contain a fixed number of addresses. Each page is stored on the disk and when that page is needed, the OS copies it from disk to main memory and translates the virtual address into real address.