Introduction to RAID disk array features

First, RAID overview

RAID is an abbreviation for the English Redundant array of independent disks, which translates into Chinese as "redundant array of independent disks" or simply as a disk array. To put it simply, RAID is a combination of several separate physical hard disks or partitions in a different way to form a unified disk group at the logical level, providing higher storage performance and redundancy than a single hard drive. The different ways to make up a disk array are called RAID levels (RAID levels), and note that the difference in levels is only that their composition is different, without the merit or disadvantage of performance.

Second, RAID classification

The implementation of RAID is divided into hard raid and soft raid two, by hardware to achieve the RAID function is hard raid, mainly through the expansion card or computer motherboard integration and other hardware implementation.

• • External disk array: Adapter capability with expansion cards

  • Internal-Connection RAID: Motherboard integrated RAID controller

Software uses CPU to complete raid called soft raid, software RAID consumes high CPU resources, most of the server devices are hardware RAID.

Iii. characteristics of each level

Here are just a few of the frequently used RAID levels: RAID-0, RAID-1, RAID-5 ...

1) RAID0

According to the "stripe" the data is divided into n equal parts, and then put the data into each disk sequentially;

• • Read and write performance improvements;

  • )  

  • no fault tolerance

  • 2, Min.

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2) RAID-1:

While reading and writing data in parallel, the original data is fully mirrored, that is, 1 copies of the data into 2 copies;

• • Read performance improvement, write performance slightly decreased;

  • free Space: 1*min (s1,s2,...)

  • Have redundancy capability

  • minimum number of disks: 2,

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3) RAID-5 :

The data write is similar to RAID0, the difference is that, RAID5 in the process of data writing, in each disk also added a same bit check data (parity), this data will record the backup data of the other disk, used to worry about the disk damage when the calculation reply;

• free space: Span style= "font-family: ' Comic Sans MS '; font-size:16px;" > (N-1) *min*n

• 1 block disk

• minimum number of disks:

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4) Mixed type

4.1) RAID10 :

• • read, write performance improvements

  • free space: n*min/2

  • Span style= "font-family: ' Comic Sans MS '; font-size:16px;" > fault tolerance: Each group of mirrors can only be broken at most;

  • 4, 4+

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4.2) RAID01:

• • • read, write performance improvements

    • Free space: n*min/2

    • fault tolerance: Each group of hard drives can only be bad 2 blocks;

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Ps:

      Create a free space for10Gof theRAID5equipment that requires itsChunksize is128k, the file system isExt4, there is a free disk, the boot can be automatically mounted to/backupdirectory;

A: The process of solving problems:fdiskCreating Partitions>=4(System type is adjusted toFD)àUsePatx(CENTOS6) command to reread the disk partition by the kernel (/proc/partitions)àUsefdisk–lTo see if the partition was successfulàUseMdadmCommand CreationRAIDàMKE2FSformatàAuto mount on boot (BlkidCheckUUIDWrite/etc/fstab)

~]# mdadm-c/dev/md0-a yes-l 5-c 128-x 1-n 3/dev/sda{5,6,7,8}

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Introduction to RAID disk array features