Friday, June 28, 2013

               
   
   
   

RAID Levels RAID0,RAID1,RAID5,RAID10,RAID01

RAID (redundant array of independent disks, originally redundant array of inexpensive disks) It’s a storage technology that combines the multiple disk drive into a logical unit and give it as a single large hard drive to the Operation system

In Raid technology Data is distributed across the drives in one of the following RAID levels

Before going to the RAID Levels Lets see some RAID concept

Data striping:
Its technique of segmenting sequential data 
Data is written in stripes across multiple disks so it's increasing performance because at a same time multiple drives are reading and writing data
For example If you have a 400 KB file and two hard disks with RAID 0 then file will be cut into two 200 KB chunks (striping) and each chunk will be written on different hard disk    

Parity:
The parity data is used to achieve the redundancy if a drive fails, the lost data will reconstruct from the parity data

Mirroring:
Disk mirroring means same data are written on each disk

RAID Levels:
We use RAID Levels depending on the redundancy and performance required

Let's see most commonly used RAID Levels

In diagram :
A, B, C & D are represented data block
P is represented parity  

RAID 0: Block-level striping without parity

  • Data is written in stripes across multiple disks without parity, no fault tolerance  
  • Minimum disk required: - 2
  • Data protection :No, If a single drive fails all data lost, Its not a true raid
  • Performance :Read / Write is high
  • Total storage capacity  : 100%

RAID 1: Mirroring without parity

  • The same data is written on two disks(raid group) simultaneously so its duplicate disk
  • Minimum disk required: - 2
  • Data protection :Yes, If a single drive fails, still no data loss
  • Performance :Read is high / Write is medium  
  • Total storage capacity  : 50%

RAID 5:Block-level striping with distributed parity

  • Data is written in stripes across multiple disks and parity also distributed on each disk so if the disk fails then replace disk will rebuild from parity data 
  • Minimum disk required: - 3
  • Data protection : Yes, If a single drive fails, still no data loss
  • Performance : Read is high / Write is Low
  • Total storage capacity  : 70-90%


RAID 10, RAID 1+0: Mirroring without parity, and block-level striping

  • RAID10 also called stripe of mirrors
  • Data is written in stripes across primary disks then It’s mirrored to the secondary disks
  • Minimum disk required: - 4
  • Data protection : Yes If single drive fails in each sub-group(array), still no data loss
  • Performance : Read is high / Write is medium
  • Total storage capacity  : 50%


RAID 0+1:
  • RAID 0+1 is also called a mirror of stripes
  • Data is written across two disks in RAID 0 and then all data is mirrored on a second RAID 0 group
  • Minimum disk required: - 4
  • Data protection : The Raid group sustains with one or more drives failed in the same mirror set, but if the drives fail on both sides of the mirror then all data is lost,
  • Fault tolerances are less comparing to RAID 10
  • Performance : Read is high / Write is medium
  • Total storage capacity  : 50%

1 comments:

  1. So short and sweet. it is easy to remember.
    Thanks for post

    ReplyDelete

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