Back up types

BACKUP TYPES

Back-up is the operation done to prevent data loss. The principle is to make copies of particular data in order to use those copies for restoring the information if a failure occurred (a data loss event due to deletion, corruption, theft etc.). The back-up can be done manually (copying the data to a different location) or automatically using a backup program, such as NTBACKU Pin windows.

There are five types of backup in windows 2003 server

1.Normal backup - It copy all the files marked in to be backup

2. Incremental backup - only those files that have been created or changed since last incremental or normal backup.

3.Differential backup - The only copies files that have been created or changed since the last normal or incremental backup

4.copy backup - It copy all the files u have selected 

5. Daily backup - It copy all the files u have selected that have been modified on the day

Each program has its own approach in executing the backup, but there are five common backup types implemented and generally used in most of these programs:A type of backup actually defines how the data is copied from the source to the destination and lays the grounds of a data repository model (how the back-up is stored and structured).

The image below provides an overview comparison between these backup types, for detailed information about each read the rest of the article:

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Full backup:Full backup is the starting point for all other types of backup and contains all the data in the folders and files that are selected to be backed up. Because full backup stores all files and folders, frequent full backups result in faster and simpler restore operations. Remember that when you choose other backup types, restore jobs may take longer. As an example, for a full backup job that runs four times the representation below is conclusive on how the backed up data will grow with every run

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Differential backup:Differential backup contains all files that have changed since the last FULL backup. The advantage of a differential backup is that it shortens restore time compared to a full backup or an incremental backup. However, if you perform the differential backup too many times, the size of the differential backup might grow to be larger than the baseline full backup. In the image below you can see an example on how a differential backup would look like for a backup job that runs four times:

Incremental backup:Incremental backup stores all files that have changed since the last FULL, DIFFERENTIAL OR INCREMENTAL backup. The advantage of an incremental backup is that it takes the least time to complete. However, during a restore operation, each incremental backup must be processed, which could result in a lengthy restore job. The representation below shows how a backup job running four times would look like when using incremental:

Mirror backup:Mirror backup is identical to a full backup, with the exception that the files are not compressed in zip files and they can not be protected with a password. A mirror backup is most frequently used to create an exact copy of the source data. It has the benefit that the backup files can also be readily accessed using tools like Windows Explorer. The image below shows how a mirror backup job would look after four iterations (first mirror will back-up everything, subsequent fast mirror backups will back-up only new/modified files):

RAID

RAID stands for Redundant Array of Inexpensive (or sometimes "Independent") Disks. RAID is a method of combining multiple hard disks in a single logical unit to offer high availability, performance or a combination of both. This provides better resilience and performance than a single disk drive.

The benefits of RAID explained

Provides real-time data recovery with uninterrupted access when a hard drive fails

• Increases system uptime and network availability
• Protects against data loss
• Multiple drives working in parallel increases system performance

Software RAID

Many operating systems provide functionality for implementing software based RAID systems.  The software RAID systems generate the RAID algorithms using the server CPU,this can severely limit the RAID performance. Should a server fail the whole RAID system is lost. Cheap to implement and only need a single SCSI controller.

Hardware RAID

All RAID algorithms are generated on the RAID controller board, thus freeing the server CPU.  Allows full benefits and data protection of RAID. More robust and fault tolerant than software RAID. Requires dedicated RAID controller to work.

Software RAID levels

1).Simple Volumes

Simple volumes are the dynamic-disk equivalent of the primary partitions and logical drives found on basic disks. When creating simple volumes, keep these points in mind:

• If you have only one dynamic disk, you can create only simple volumes.
• You can increase the size of a simple volume to include unallocated space on the same disk or on a different disk. The volume must be unformatted or formatted by using NTFS. You can increase the size of a simple volume in two ways:
• By extending the simple volume on the same disk. The volume remains a simple volume, and you can still mirror it.
• By extending a simple volume to include unallocated space on other disks on the same computer. This creates a spanned volume.
  
  Note

If the simple volume is the system volume or the boot volume, you cannot extend it.

2).Spanned Volumes

Spanned volumes combine areas of unallocated space from multiple disks into one logical volume. The areas of unallocated space can be different sizes. Spanned volumes require two disks, and you can use up to 32 disks. When creating spanned volumes, keep these points in mind:

• You can extend only NTFS volumes or unformatted volumes.
• After you create or extend a spanned volume, you cannot delete any portion of it without deleting the entire spanned volume.
• You cannot stripe or mirror spanned volumes. For more information about striped or mirrored volumes, see “Striped Volumes” or “Mirrored Volumes” later in this section.
• Spanned volumes do not provide fault tolerance. If one of the disks containing a spanned volume fails, the entire volume fails, and all data on the spanned volume becomes inaccessible. The reliability for a spanned volume is less than the least reliable disk in the set.

3).Striped Volumes

Striped volumes improve disk input/output (I/O) performance by distributing I/O requests across disks. Striped volumes are composed of stripes of data of equal size written across each disk in the volume. They are created from equally sized, unallocated areas on two or more disks. In Windows Server 2003, the size of each stripe is 64 kilobytes (KB) and cannot be changed.

Striped volumes cannot be extended or mirrored and do not offer fault tolerance. If one of the disks containing a striped volume fails, the entire volume fails, and all data on the striped volume becomes inaccessible. The reliability for the striped volume is less than the least reliable disk in the set.

RAID LEVEL 0

Following are the key points to remember for RAID level 0.

• Minimum 2 disks.
• Excellent performance ( as blocks are striped ).
• No redundancy ( no mirror, no parity ).
• Don’t use this for any critical system.

4).Mirrored Volumes

A mirrored volume is a fault-tolerant volume that provides a copy of a volume on another disk. Mirrored volumes provide data redundancy by duplicating the information contained on the volume. The two disks that make up a mirrored volume are known as mirrors. Each mirror is always located on a different disk. If one of the disks fails, the data on the failed disk becomes unavailable, but the system continues to operate by using the unaffected disk.

Mirrored volumes are available only on computers running the Windows 2000 Server family or Windows Server 2003.

RAID LEVEL 1

Following are the key points to remember for RAID level 1.

• Minimum 2 disks.
• Good performance ( no striping. no parity ).
• Excellent redundancy ( as blocks are mirrored ).

5).RAID-5 Volumes

A RAID-5 volume is a fault-tolerant volume that stripes data and parity across three or more disks. Parity is a calculated value that is used to reconstruct data if one disk fails. When a disk fails, Windows Server 2003 continues to operate by recreating the data that was on the failed disk from the remaining data and parity. RAID-5 volumes are available only on computers running the Windows 2000 Server family or Windows Server 2003.

RAID LEVEL 5

Following are the key points to remember for RAID level 5.

• Minimum 3 disks.
• Good performance ( as blocks are striped ).
• Good redundancy ( distributed parity ).
• Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.