Raid

[forumdude123]

Can i run 3 hard drives in RAID0? what is the difference between raid 0+1 and raid 1+0. Can someone please explain this clearly, because the websites make it difficult to understand??!!

[Michael_Knight]

Raid 0 is basically for Striping, and is usually for 2 HDD's

There are at least nine types of RAID plus a non-redundant array (RAID-0):

• RAID-0: This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.
• RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.
• RAID-2: This type uses striping across disks with some disks storing error checking and correcting (ECC) information. It has no advantage over RAID-3.
• RAID-3: This type uses striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used to detect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives. Since an I/O operation addresses all drives at the same time, RAID-3 cannot overlap I/O. For this reason, RAID-3 is best for single-user systems with long record applications.
• RAID-4: This type uses large stripes, which means you can read records from any single drive. This allows you to take advantage of overlapped I/O for read operations. Since all write operations have to update the parity drive, no I/O overlapping is possible. RAID-4 offers no advantage over RAID-5.
• RAID-5: This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.
• RAID-6: This type is similar to RAID-5 but includes a second parity scheme that is distributed across different drives and thus offers extremely high fault- and drive-failure tolerance.
• RAID-7: This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of a stand-alone computer. One vendor offers this system.
• RAID-10: Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In RAID-1+0, the data is mirrored and the mirrors are striped.
• RAID-50 (or RAID-5+0): This type consists of a series of RAID-5 groups and striped in RAID-0 fashion to improve RAID-5 performance without reducing data protection.
• RAID-53 (or RAID-5+3): This type uses striping (in RAID-0 style) for RAID-3's virtual disk blocks. This offers higher performance than RAID-3 but at much higher cost.
• RAID-S (also known as Parity RAID): This is an alternate, proprietary method for striped parity RAID from EMC Symmetrix that is no longer in use on current equipment. It appears to be similar to RAID-5 with some performance enhancements as well as the enhancements that come from having a high-speed disk cache on the disk array.

What is Striping...

In computers that use multiple hard disk systems, disk striping is the process of dividing a body of data into blocks and spreading the data blocks across several partitions on several hard disks. Each stripe is the size of the smallest partition. For example, if three partitions are selected with one partition equaling 150megabytes, another 100MB, and the third 50MB, each stripe will be 50 MB in size. It is wise to create the partitions equal in size to prevent wasting disk space. Each stripe created is part of the stripe set. Disk striping is used with redundant array of independent disks (RAID). RAID is a storage system that uses multiple disks to store and distribute data. Up to 32 hard disks can be used with disk striping.

There are two types of disk striping: single user and multi-user. Single user disk striping allows multiple hard disks to simultaneously service multiple I/O requests from a single workstation. Multi-user disk striping allows multiple I/O requests from several workstations to be sent to multiple hard disks. This means that while one hard disk is servicing a request from a workstation, another hard disk is handling a separate request from a different workstation.

Disk striping is used with or without parity. When disk striping is used with parity, an additional stripe that contains the parity information is stored on its own partition and hard disk. If a hard disk fails, a fault tolerance driver makes the lost partition invisible allowing reading and writing operations to continue which provides time to create a new stripe set. Once a hard disk fails, the stripe set is no longer fault tolerant, which means that if one or more hard disks fail after the first one, the stripe set is lost. Disk striping without parity provides no fault tolerance. The disk striping process is used in conjunction with software that lets the user know when a disk has failed. This software also allows the user to define the size of the stripes, the colour assigned to the stripe set for recognition and diagnosing, and whether parity was used or not.

Disk Mirroring...

As it states, Mirroring creates a mirror image/copy of a drive.

[forumdude123]

Raid 0 is basically for Striping, and is usually for 2 HDD's

There are at least nine types of RAID plus a non-redundant array (RAID-0):

• RAID-0: This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.
• RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.
• RAID-2: This type uses striping across disks with some disks storing error checking and correcting (ECC) information. It has no advantage over RAID-3.
• RAID-3: This type uses striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used to detect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives. Since an I/O operation addresses all drives at the same time, RAID-3 cannot overlap I/O. For this reason, RAID-3 is best for single-user systems with long record applications.
• RAID-4: This type uses large stripes, which means you can read records from any single drive. This allows you to take advantage of overlapped I/O for read operations. Since all write operations have to update the parity drive, no I/O overlapping is possible. RAID-4 offers no advantage over RAID-5.
• RAID-5: This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.
• RAID-6: This type is similar to RAID-5 but includes a second parity scheme that is distributed across different drives and thus offers extremely high fault- and drive-failure tolerance.
• RAID-7: This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of a stand-alone computer. One vendor offers this system.
• RAID-10: Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In RAID-1+0, the data is mirrored and the mirrors are striped.
• RAID-50 (or RAID-5+0): This type consists of a series of RAID-5 groups and striped in RAID-0 fashion to improve RAID-5 performance without reducing data protection.
• RAID-53 (or RAID-5+3): This type uses striping (in RAID-0 style) for RAID-3's virtual disk blocks. This offers higher performance than RAID-3 but at much higher cost.
• RAID-S (also known as Parity RAID): This is an alternate, proprietary method for striped parity RAID from EMC Symmetrix that is no longer in use on current equipment. It appears to be similar to RAID-5 with some performance enhancements as well as the enhancements that come from having a high-speed disk cache on the disk array.

What is Striping...

In computers that use multiple hard disk systems, disk striping is the process of dividing a body of data into blocks and spreading the data blocks across several partitions on several hard disks. Each stripe is the size of the smallest partition. For example, if three partitions are selected with one partition equaling 150megabytes, another 100MB, and the third 50MB, each stripe will be 50 MB in size. It is wise to create the partitions equal in size to prevent wasting disk space. Each stripe created is part of the stripe set. Disk striping is used with redundant array of independent disks (RAID). RAID is a storage system that uses multiple disks to store and distribute data. Up to 32 hard disks can be used with disk striping.

There are two types of disk striping: single user and multi-user. Single user disk striping allows multiple hard disks to simultaneously service multiple I/O requests from a single workstation. Multi-user disk striping allows multiple I/O requests from several workstations to be sent to multiple hard disks. This means that while one hard disk is servicing a request from a workstation, another hard disk is handling a separate request from a different workstation.

Disk striping is used with or without parity. When disk striping is used with parity, an additional stripe that contains the parity information is stored on its own partition and hard disk. If a hard disk fails, a fault tolerance driver makes the lost partition invisible allowing reading and writing operations to continue which provides time to create a new stripe set. Once a hard disk fails, the stripe set is no longer fault tolerant, which means that if one or more hard disks fail after the first one, the stripe set is lost. Disk striping without parity provides no fault tolerance. The disk striping process is used in conjunction with software that lets the user know when a disk has failed. This software also allows the user to define the size of the stripes, the colour assigned to the stripe set for recognition and diagnosing, and whether parity was used or not.

Disk Mirroring...

As it states, Mirroring creates a mirror image/copy of a drive.

Thanks, you were a big help!! I will use raid 0. :)

[Michael_Knight]

Hey, you're welcome.