RAID (Redundant Array of Independent Disks) is a common storage technology and is widely used on CentOS servers. RAID can achieve data redundancy, read and write acceleration, or capacity integration through the combination of multiple hard disks.

Before deploying RAID on a CentOS server, you first need to clarify the characteristics and application scenarios of different RAID levels. The following is an introduction to several commonly used RAID levels:

RAID 0: Data striping, no redundancy, mainly used to improve read and write performance, but any damage to the hard disk will cause data loss.

RAID 1: Mirror mode, two hard disks back up each other, high data security, and halved capacity.

RAID 5: At least three hard disks are required, data redundancy is achieved through parity check, read performance is good, but write performance is limited.

RAID 10 (1+0): Combining RAID 1 and RAID 0, performance and security are balanced, and at least four hard disks are required.

When choosing a RAID level, you should consider the purpose of the server, budget, and data importance. For example, RAID 10 is usually recommended for game server databases, while RAID 5 may be used for large-capacity storage.

Preparation and environment description

Before starting the CentOS server RAID configuration, you need to make the following preparations:

Hardware check: confirm the number, capacity, and interface type (SATA, SAS, NVMe, etc.) of server hard disks.

RAID type selection: determine whether to use soft RAID (mdadm configuration) or hard RAID (RAID controller card configuration).

System version: This article takes CentOS 7/8 as an example and is applicable to most mainstream versions.

Data backup: If you are configuring RAID for an existing hard disk, you must back up the data in advance to prevent data loss during the operation.

Configure software RAID using the mdadm tool

For CentOS servers without hardware RAID cards, you can use the built-in mdadm tool to create a soft RAID. The following takes RAID 1 (mirror mode) as an example to introduce the specific operation steps.

Install the mdadm tool

First, make sure mdadm is installed. If not, you can install it with the following command:

yum install mdadm -y # CentOS 7/8

Create RAID device

Assuming there are two empty hard disks /dev/sdb and /dev/sdc on the server, you can execute the following command to create RAID 1:

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc

Parameter description:

/dev/md0: the name of the newly created RAID device.

--level=1: specifies RAID 1.

--raid-devices=2: the number of hard disks in the RAID.

The creation process may prompt for confirmation, enter yes to continue.

Check RAID status

After creation, check the RAID status with the following command:

cat /proc/mdstat

If the output shows that md0 is syncing, the RAID array was created successfully and data is being synchronized.

Format and mount the RAID device

After synchronization is complete, format and mount the RAID device:

mkfs.ext4 /dev/md0
mkdir /raid1
mount /dev/md0 /raid1

In order to automatically mount at boot, you need to write the information to /etc/fstab:

echo "/dev/md0 /raid1 ext4 defaults 0 0" >> /etc/fstab

Save RAID configuration

In order to automatically activate the RAID array after the system restarts, you need to save the configuration:

mdadm --detail --scan >> /etc/mdadm.conf

CentOS 8 system can use /etc/mdadm.conf or /etc/mdadm/mdadm.conf, and adjust according to the actual situation.

Brief description of RAID hardware card configuration

If the server is equipped with a hardware RAID card (such as DELL PERC, HP Smart Array, etc.), it is recommended to configure it through the RAID card's built-in management tool or BIOS interface. This type of RAID card usually has a configuration menu when the server starts up. The operation interface is intuitive and supports advanced functions such as array creation, disk hot backup, and hard disk detection.

After the configuration is completed, the operating system will only recognize the RAID array as a logical disk, and there is no need to create RAID at the system level.

Monitoring and management of RAID arrays

After the RAID array is deployed, daily maintenance and monitoring are very important. You can use the following command to check the health status of the RAID regularly:

mdadm --detail /dev/md0

For hardware RAID arrays, you need to use tools provided by the RAID manufacturer or monitor disk health through SNMP, email alerts, etc.

At the same time, it is recommended to enable regular inspection tasks to perform consistency checks on the RAID array:

echo check > /sys/block/md0/md/sync_action

You can combine crontab to implement periodic checks, and log the results for future reference.

RAID configuration precautions

There are several common misunderstandings and precautions when actually configuring the CentOS server RAID array:

RAID is not a backup: Even if you use arrays with redundancy functions such as RAID 1 and RAID 5, they cannot replace offsite backup or cloud backup.

Be cautious when replacing hard disks: When replacing hard disks in a degraded array state, you must strictly follow the process to avoid data loss or array crash.

Monitoring must be in place: Especially for multi-disk arrays such as RAID 5 and RAID 6, timely processing is crucial when a single disk failure occurs.

Reasonable performance expectations: The performance of soft RAID is slightly inferior to that of hard RAID under high IO pressure, and a reasonable assessment should be made based on business needs before deployment.

Consistency checks cannot be omitted: Regularly checking RAID consistency helps to detect potential disk failures in advance and avoid data damage.

Configuring RAID disk arrays on CentOS servers is an important means to improve data security and storage performance. Whether you choose soft RAID or hard RAID, you need to be meticulous and standardized in all aspects from planning, deployment to operation and maintenance. Only by properly selecting RAID levels, doing a good job of data backup, and establishing a comprehensive monitoring mechanism can we ensure that applications such as game servers, enterprise databases, and big data platforms remain stable and reliable in the face of high loads and hardware failures.