Hello World,
I am here again with a common topic RAID.I know it is a vast subject .I just try to disscuss it with a Nutshell.
So we all know RAID = Redundant array of independent disks or originally redundant array of inexpensive disks.What is this?
Actually It is a great way of storing data on multiple disk or in different place on network.Since multiple disks increases the mean time between failures (MTBF).
RAID technology was first defined by a group of computer scientists at the University of California at Berkeley in 1987.
Now a days Mainly 3 types of Array used in RAID technology.They are as follow.
Software based Raid
Primarily used with entry-level servers, software-based arrays rely on a standard host adapter and execute all I/O commands and mathematically intensive RAID algorithms in the host server CPU.only used for low price and less component require.
Hardware based RAID
Hardware-based RAID uses an intelligent drive controller and a redundant array of disk drives to protect against data loss in the event of media failure and to improve the performance of read/write operations. A disk array is an effective disk-storage solution for computers running database software.
External Hardware RAID Card
Intelligent external array controllers "bridge" between one or more server I/O interfaces and single- or multiple-device channels.
There are mainly 2 types of RAID Level like Standard RAID and Nested or Hybrid RAID.Standard RAID include RAID 0, RAID 1, RAID 2, RAID 3, RAID 4, RAID 5, RAID 6 , RAID 7.
RAID 0
Mechanism Used = Striping but no redundancy of data.
Minimum Disk Required = 2
Advantage = Improve performance and speed.
Disadvantage = No fault tolerance.
RAID 1
Mechanism Used = Mirroring or exact copy of date
Minimum Disk Required = 2
Advantage = Improve read performance and great fault tolerance for malty user system
Disadvantage =Effective storage capacity become half and in software Raid we cannot use Hot swap disk management.
RAID 2
Mechanism Used = Bit-level striping with dedicated Hamming-code parity or binary linear codes with error correction parity.
Minimum Disk Required = 3
Advantage =It can recover from 1 drive failure or repair corrupt data or parity when a corrupted bit's corresponding data and parity are good
Disadvantage =Entry level cost very high - requires very high transfer data rate.
RAID 3
Mechanism Used = Byte level striping and dedicates one drive to storing parity information.
Minimum Disk Required = 3
Advantage = High throughput for large data transfer.
Disadvantage =RAID-3 cannot overlap I/O. Very complex mechanism use and heavy resources used.
RAID 4
Mechanism Used = Block level striping with parity.
Minimum Disk Required = 3
Advantage =The cost per megabyte of a RAID 4 array is low because only one drive in the array stores redundant data and read speed is good.
Disadvantage =Does not support multiple simultaneous write operations.
RAID 5
Mechanism Used = Block level striping with distributed parity
Minimum Disk Required = 3
Advantage =Read data transactions are very fast but write data speed is quite slow
Disadvantage =complex mechanism used as like RAID 3.
RAID 6
Mechanism Used = This type is similar to RAID-5 but includes a second parity scheme.Used XOR parity generation and Read Solomon ECC Generation.
Minimum Disk Required = 4
Advantage =extremely high data fault tolerance and can sustain multiple simultaneous drive failures.
Disadvantage =It is quite expensive as a special controller is required for it.The dual parity checks increases the complex calculations due to which the system performance
RAID 7
RAID 7 is a Non Industry Standard proprietary product of a single company.
It is mixed of a real-time embedded operating system as a controller with a caching via a high-speed dedicated bus.The controller card uses its own CPU and combines striping and RAID-5-like storage.
Hybrid RAID or Nested RAID
It is a combination of different standard level RAID used to increase high speed data throughput (Read and Write),disk space manage and fault tolerance maintaining. They are also sometimes called two-dimensional.
RAID 0+1
Mechanism Used = First the data are striped and next it mirrored.
Minimum Disk Required =4
Advantage = Higher performance than RAID 5 and easy installation
Disadvantage =Inefficient of usable disk space and costly
RAID 1+0
Mechanism Used = combination of RAID 1 and RAID 0. First Mirrored and Mirrored set distributed as block or striped.
Minimum Disk Required = 4
Advantage = High speed and good data security
Disadvantage =costly and complex mechanism
RAID 50
Mechanism Used = consist of series od RAID 5 and next striped.
Minimum Disk Required = 6
Advantage = It can sustain one to four drive failures while maintaining data integrity if each failed disk is in a different RAID 5 array.
Disadvantage =very expensive
RAID 53
Mechanism Used = Mirrored striped set with parity.
Minimum Disk Required = 5
Advantage = Very good I/O throughput for both data read and wright process
Disadvantage =Expensive and critical mechanism implied
There are so many Non-Standard level RAID :
•Double parity
•RAID DP
•RAID 1.5
•1.4 RAID 5E, RAID 5EE and RAID 6E
•1.5 RAID S or Parity RAID
•1.6 Intel Matrix RAID
•1.7 Linux MD RAID 10
•1.8 IBM ServeRAID 1E
•1.9 RAID-K
•1.10 RAID-Z
•1.11 Tahoe Distributed File System
•1.12 Drive Extender
•1.13 Drobo BeyondRAID
Fault Tolerance in RAID
There are mainly 4 types of Fault Tolerance.They are as follow.......
MTDL:
Mean Time to Data Loss. The average time before the failure of an array component causes data to be lost or corrupted.
MTDA:
Mean Time between Data Access (or availability). The average time before non-redundant components fail, causing data inaccessibility without loss or corruption.
MTTR:
Mean Time To Repair. The average time required to bring an array storage subsystem back to full fault tolerance.
MTBF:
Mean Time Between Failure. Used to measure computer component average reliability/life expectancy.
Mainly 3 types of Disk technology is used in RAID. They are as follow.
Hot Plug Disk
we can plug or unplug and Hard disk when the system is running. System can recognized and identify it.Mainly USB and IEEE 1394 can support it.
Hot swap Disk
Hot swapping is used whenever it is desirable to change the configuration or repair a working system without interrupting its operation.we can apply Raid technology on it and repair.
Hot Spare Disk
Hot spares are a good addition to a fault-tolerant array. They greatly reduce the impact of monitoring on the array reliability. when needed it added to the system to backup the server and when we repair the disk or change a new drive with a Hot plug or Hot swap technology it turns back to it idle state.
RAID technology apply
RAID 0 =RAID 0 is not really a "true" RAID system, as there is no fault tolerance involved here.
RAID 1 =Small Database system for Accounting service or Office uses.
RAID 5 =File and Application server, WWW, Intranet server
RAID 6 =Data Warehousing .
RAID 10 =High capacity disk, Internet server, SQL server
RAID 50 =File and Application server, Transaction processing, High capacity disk storage
I am here again with a common topic RAID.I know it is a vast subject .I just try to disscuss it with a Nutshell.
So we all know RAID = Redundant array of independent disks or originally redundant array of inexpensive disks.What is this?
Actually It is a great way of storing data on multiple disk or in different place on network.Since multiple disks increases the mean time between failures (MTBF).
RAID technology was first defined by a group of computer scientists at the University of California at Berkeley in 1987.
Now a days Mainly 3 types of Array used in RAID technology.They are as follow.
Software based Raid
Primarily used with entry-level servers, software-based arrays rely on a standard host adapter and execute all I/O commands and mathematically intensive RAID algorithms in the host server CPU.only used for low price and less component require.
Hardware based RAID
Hardware-based RAID uses an intelligent drive controller and a redundant array of disk drives to protect against data loss in the event of media failure and to improve the performance of read/write operations. A disk array is an effective disk-storage solution for computers running database software.
External Hardware RAID Card
Intelligent external array controllers "bridge" between one or more server I/O interfaces and single- or multiple-device channels.
There are mainly 2 types of RAID Level like Standard RAID and Nested or Hybrid RAID.Standard RAID include RAID 0, RAID 1, RAID 2, RAID 3, RAID 4, RAID 5, RAID 6 , RAID 7.
RAID 0
Mechanism Used = Striping but no redundancy of data.
Minimum Disk Required = 2
Advantage = Improve performance and speed.
Disadvantage = No fault tolerance.
RAID 1
Mechanism Used = Mirroring or exact copy of date
Minimum Disk Required = 2
Advantage = Improve read performance and great fault tolerance for malty user system
Disadvantage =Effective storage capacity become half and in software Raid we cannot use Hot swap disk management.
RAID 2
Mechanism Used = Bit-level striping with dedicated Hamming-code parity or binary linear codes with error correction parity.
Minimum Disk Required = 3
Advantage =It can recover from 1 drive failure or repair corrupt data or parity when a corrupted bit's corresponding data and parity are good
Disadvantage =Entry level cost very high - requires very high transfer data rate.
RAID 3
Mechanism Used = Byte level striping and dedicates one drive to storing parity information.
Minimum Disk Required = 3
Advantage = High throughput for large data transfer.
Disadvantage =RAID-3 cannot overlap I/O. Very complex mechanism use and heavy resources used.
RAID 4
Mechanism Used = Block level striping with parity.
Minimum Disk Required = 3
Advantage =The cost per megabyte of a RAID 4 array is low because only one drive in the array stores redundant data and read speed is good.
Disadvantage =Does not support multiple simultaneous write operations.
RAID 5
Mechanism Used = Block level striping with distributed parity
Minimum Disk Required = 3
Advantage =Read data transactions are very fast but write data speed is quite slow
Disadvantage =complex mechanism used as like RAID 3.
RAID 6
Mechanism Used = This type is similar to RAID-5 but includes a second parity scheme.Used XOR parity generation and Read Solomon ECC Generation.
Minimum Disk Required = 4
Advantage =extremely high data fault tolerance and can sustain multiple simultaneous drive failures.
Disadvantage =It is quite expensive as a special controller is required for it.The dual parity checks increases the complex calculations due to which the system performance
RAID 7
RAID 7 is a Non Industry Standard proprietary product of a single company.
It is mixed of a real-time embedded operating system as a controller with a caching via a high-speed dedicated bus.The controller card uses its own CPU and combines striping and RAID-5-like storage.
Hybrid RAID or Nested RAID
It is a combination of different standard level RAID used to increase high speed data throughput (Read and Write),disk space manage and fault tolerance maintaining. They are also sometimes called two-dimensional.
RAID 0+1
Mechanism Used = First the data are striped and next it mirrored.
Minimum Disk Required =4
Advantage = Higher performance than RAID 5 and easy installation
Disadvantage =Inefficient of usable disk space and costly
RAID 1+0
Mechanism Used = combination of RAID 1 and RAID 0. First Mirrored and Mirrored set distributed as block or striped.
Minimum Disk Required = 4
Advantage = High speed and good data security
Disadvantage =costly and complex mechanism
RAID 50
Mechanism Used = consist of series od RAID 5 and next striped.
Minimum Disk Required = 6
Advantage = It can sustain one to four drive failures while maintaining data integrity if each failed disk is in a different RAID 5 array.
Disadvantage =very expensive
RAID 53
Mechanism Used = Mirrored striped set with parity.
Minimum Disk Required = 5
Advantage = Very good I/O throughput for both data read and wright process
Disadvantage =Expensive and critical mechanism implied
There are so many Non-Standard level RAID :
•Double parity
•RAID DP
•RAID 1.5
•1.4 RAID 5E, RAID 5EE and RAID 6E
•1.5 RAID S or Parity RAID
•1.6 Intel Matrix RAID
•1.7 Linux MD RAID 10
•1.8 IBM ServeRAID 1E
•1.9 RAID-K
•1.10 RAID-Z
•1.11 Tahoe Distributed File System
•1.12 Drive Extender
•1.13 Drobo BeyondRAID
Fault Tolerance in RAID
There are mainly 4 types of Fault Tolerance.They are as follow.......
MTDL:
Mean Time to Data Loss. The average time before the failure of an array component causes data to be lost or corrupted.
MTDA:
Mean Time between Data Access (or availability). The average time before non-redundant components fail, causing data inaccessibility without loss or corruption.
MTTR:
Mean Time To Repair. The average time required to bring an array storage subsystem back to full fault tolerance.
MTBF:
Mean Time Between Failure. Used to measure computer component average reliability/life expectancy.
Mainly 3 types of Disk technology is used in RAID. They are as follow.
Hot Plug Disk
we can plug or unplug and Hard disk when the system is running. System can recognized and identify it.Mainly USB and IEEE 1394 can support it.
Hot swap Disk
Hot swapping is used whenever it is desirable to change the configuration or repair a working system without interrupting its operation.we can apply Raid technology on it and repair.
Hot Spare Disk
Hot spares are a good addition to a fault-tolerant array. They greatly reduce the impact of monitoring on the array reliability. when needed it added to the system to backup the server and when we repair the disk or change a new drive with a Hot plug or Hot swap technology it turns back to it idle state.
RAID technology apply
RAID 0 =RAID 0 is not really a "true" RAID system, as there is no fault tolerance involved here.
RAID 1 =Small Database system for Accounting service or Office uses.
RAID 5 =File and Application server, WWW, Intranet server
RAID 6 =Data Warehousing .
RAID 10 =High capacity disk, Internet server, SQL server
RAID 50 =File and Application server, Transaction processing, High capacity disk storage