What is Virtual memory – explained

Disk storage used to expand the capacity of RAM

When RAM is exceeded, virtual memory is treated as if it were RAM

Uses paging technique

  Pages are blocks of information moved from RAM into virtual memory

On a Pentium computer, blocks are 4 KB

 Pages are moved back into RAM when needed
A paging file is the area of disk allocated for virtual memory

   Initial and maximum size of the paging file
                      Set initial size to at least 1.5 times RAM
           Set maximum size to twice the initial size

                       Do not place the paging file on the boot partition

            Place a paging file on each disk (except the boot partition)

            Place paging file on main disk for a mirrored set or volume

            Do not place a paging file on a stripe set or volume, or RAID-5 volume

DIfference Between Peer to Peer and Server based networking

Peer-to-peer networking

•          Designed for ten or less workstations

•          Only moderate network security

–        Users manage their own account information.

•          No centralized storage of information

•          No centralized administration control

–        Lack of management for users and critical files

–        Inability to centrally back up important files

•          Slower response times when sharing resources

Server-based Networking

•          Users log in once to access resources.

•          Stronger security because of server management

•          Shared files by members

•          Shared printers and other resources

•          E-mail capability through an email server

•          Applications stored in a central location

•          Backups scheduled and performed from a central location

•          Shared resources can reflect the work patterns of subgroups.

•          More efficient software upgrades 

Backup types and how to take backup

1) Normal Backup:

- Backup all files and folder after backup it rename ARCHIVE Bit

2) Daily Backup:

- Backup all selected files and folders which created or modified on daily raises. After backup it does not remove ARCHIVE Bit.

3) Copy Backup:

- Backups all selected files and folders after backup it will not remove ARCHIVE Bit.

4) Incremental Backup:

 - Backup all selected file and folders which are created or modified after last backup. After backup it does not remove ARCHIVE Bit.

Normal Backup:

-         we take normal backup the first time only because the normal backup take all file or folder to backup>

How to Take Backup:

1-     Start – Program – Accessories – System Tools – Backup.

2-     Select backup wizard then next.

3-     Select Backup select files, drive, or network data (if you want to take backup for files data drive) click next. Backup media of file name d:\backup.bkf. next finish.

Incremental Backup:

-         After take normal backup after that time we can take incremental backup because the incremental backup it will take only which file or folder you are created or modify.

How to take incremental Backup?

-        Start – run ntbackup, you will get wizard, click next

-        Backup wizard advanced, next, select your folder you want take backup, next, Browse, Completing the Backup Wizard, Advanced, Finish, Click Advanced, Type of Backup, Select Incremental, Next, Append this backup to the existing, Later, any name can give, OK.

What is Active Directory replication ?

Active Directory replication is like pull rather than push; it means that replicates pull changes from the server where the changes are affected. The Knowledge Consistency Checker (KCC) creates a replication topology of site links using the defined sites to manage traffic. Intrasite replication is frequent and automatic as a result of change notification, which triggers peers to begin a pull replication cycle. Intersite replication intervals are typically less frequent and does not use change notification by default, although this is configurable and can be made identical to intrasite replication.

Each link can have a 'cost' and the site link topology will be altered accordingly by the KCC. Replication may occur transitively through several site links on same-protocol site link bridges, if the cost is low, although KCC automatically costs a direct site-to-site link lower than transitive connections. Site-to-site replication can be configured to occur between bridgehead servers in each site, which then replicates the changes to other DCs within the site.

Replication of Active Directory uses Remote Procedure Calls (RPC) over IP (RPC/IP). Between Sites you can use SMTP for replication, but only for changes in the Schema, Configuration, or Partial Attribute Set (Global Catalog) NCs. SMTP cannot be used for replicating the default Domain partition..

Difference Between Authentication and Authorization

Authentication :-

The Web server containing the sales reports asks her workstation, “Who’s asking for this data?” The workstation replies, “rose.” The server then says, “Prove it.” So the workstation pops up a dialog box on Ivana’s screen asking for her username and password. She types in her name and password, and assuming that she types them correctly, the server then checks that name and password against a list of known users and passwords and finds that she is indeed Ivana.

Authorization :-

The mere fact that she has proven that she’s Ivana may not be sufficient reason for the Web server to give her access to the sales pages. The Web server then looks at another list sometimes known as the access control list, a list of people and access levels—“Andro can look at this page but can’t change it,” “Suse can look at this page and can change it,” “Thomas can’t look at this page at all.” Presuming rose on the “can look” list, the server sends the requested pages to her browser.

How to get last login time for Active Directory users

Copy the below code and save it as .vbs extension on desktop. You should change the second line, need to type your domain name

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Active Directory Database and Log Files

Extensible Storage Engine (ESE) is the active directory database, which manage all the active directory objects in active directory database. Any of the data modification affects database performance, database fragmentation and data integrity

The ESE uses transaction and log files to ensure the integrity of the active directory database. Active Directory includes the following files:

*    Ntds.dit is the Active Directory database which stores the entire active directory objects on the domain controller. The .dit extension refers to the directory information tree. The default location is the %systemroot%Ntds folder. Active Directory records each and every transaction log files that are associated with the Ntds.dit file

*     Edb*.log is the transaction log file. Each transaction file is 10 megabytes (MB). When Edb.log file is full, active directory renames it to Edbnnnnn.log, where nnnnn is an increasing number starts from 1.

*      Edb.chk is a checkpoint file which is use by database engine to track the data which is not yet written to    

       the active directory database file. The checkpoint file act as a pointer that maintains the status between   

       memory and database file on disk. It indicates the starting point in the log file from which the information 

       must be recovered if a failure occurs.

*       Res1.log and Res2.log: These are reserved transaction log files. The amount of disk space that is reserved 

       on a drive or folder for this log is 20 MB. This reserved disk space provides a sufficient space to shut down if 

       all the other disk space is being used.