Configure Software RAID in CentOS 6.3)

I. Introduction to RAID

RAID is the abbreviation of Redundant Array of Independent Disks ).

To put it simply, RAID combines multiple independent hard disks (physical hard disks) in different ways to form a hard disk group (logical hard disks ), this provides higher storage performance than a single hard disk and Data Backup technology.

RAID Levels is used to form disk arrays. RAID Levels include RAID 0, RAID 1, RAID 5, and RAID 10. The levels are compared as follows:

RAID level	Minimum Hard Disk	Maximum Fault Tolerance	Available capacity	Read Performance	Write Performance	Security	Purpose	Application Industry
0	2	0	N	N	N	One hard disk is abnormal. All hard disks are abnormal.	Maximum capacity and speed	Real-time 3D rendering and video editing Cache
1	2	N-1	1	N	1	The maximum value is normal.	Maximum Security	Personal and Enterprise Backup
5	3	1	N-1	N-1	N-1	High	Maximum capacity and minimum budget	Personal and Enterprise Backup
10	4	N/2	N/2	N	N/2	High Security	Combining the advantages of RAID 0/1, the theoretical speed is faster	Large Databases and servers

Note:N indicates the total number of hard disks.

For more information about RAID, see: http://zh.wikipedia.org/wiki/RAID

Ii. System Environment

Lab environment:Oracle VM VirtualBox

System Platform:CentOS release 6.3 (Final)

Mdadm version:Mdadm-v3.2.6-25th October 2012

3. Set Disks

In the Oracle VM VirtualBox, increase the number of physical disks. In this article, we will create RAID 0, RAID 1, and RAID 5 partitions. RAID 0 requires two hard disks and RAID 1 requires two hard disks, RAID5 requires four hard disks, so eight physical hard disks are added here, each of which is 5.00 GB.

4. Install mdadm

Mdadm is short for multiple devices admin. It is a standard software RAID management tool in Linux.

4.1 check whether mdadm software is installed

# Rpm-qa | grep mdadm

5. Create RAID0

5.1 create a partition

Two hard disks are required to create RAID0, so we will use/dev/sdb and/dev/sdc for the experiment.

# Fdisk/dev/sdb // partition sdb

Enter "m", get help, and enter "p" to view the disk status before partitioning. For details about other Command actions, Google and Baidu.

6. Create RAID1

Similar to creating raid0, we use the/dev/sdd and/dev/sde hard disks for experiments.

6.1 create a new partition and modify the partition type

7. Create RAID5

RAID5 requires at least three hard disks. We will test the hard disks/dev/sdf,/dev/sdg,/dev/sdh,/dev/sdi, three disks are used as active disks and the other as hot spare disks.

7.1 create a new partition and modify the partition type

The partition result is as follows:

7.4 add raid5 to the RAID configuration file/etc/mdadm. conf and modify

# Echo DEVICE/dev/sd {f, g, h, I} 1>/etc/mdadm. conf

# Mdadm-Ds>/etc/mdadm. conf

VIII. RAID Maintenance

After completing RAID, we also need to perform routine maintenance operations. For example, if one of the hard disks is damaged, we need to replace the faulty disks, the following describes how to maintain soft RAID by simulating disk corruption in RAID 5.

8.1 disk Damage Simulation

In practice, when soft RAID detects a disk failure, it will automatically mark the disk as a faulty disk and stop read/write operations on the faulty disk. Here we simulate/dev/sdh1 as a faulty disk. The command is as follows:

# Mdadm/dev/md5-f/dev/sdh1

9. Add storage hard disks to RAID

If the RAID space is not enough, we can add a new hard disk to it to increase the RAID space.

9.1 Add a physical hard disk to a VM

We have already added eight hard disks to the VM. We need to simulate new hard disks here. So we need to first disable the VM and then add a 5 Gb hard disk to the storage. Then partition and other operations. We will not repeat them here.

10. References

• Yu Fei blog: http://www.opsers.org/base/learning-linux-the-day-that-the-system-configuration-in-the-rhel6-disk-array-raid.html

 

David Camp

• For technical exchange, add the QQ group:

System O & M Technology: 296513821

• Author: QQ: 562866602
• My ID: mchina_tang
• Write to me: mchina_tang@qq.com
• My address: Suzhou, Jiangsu Province

We always believe that sharing is a virtue |We Believe, Great People Share Knowledge...