Manage your software RAIDs, Hostripples Web Hosting

Manage your software RAIDs

RAID: You must know about RAIDs if you are in hosting industry. As client or as an server admin. As a client, we must have idea about various types of RAIDs with their functionality and advantages-disadvantages then n then only we can choose best server hardware for us. Sysadmin must know the RAID administration part, to provide best quality support to premium clients.

Manage your software RAIDs, Hostripples Web Hosting

RAID types: Basically, there are 2 types of RAIDs available.

1. Hardware Raid : Its managed by hardware RAID controller.

Eg. 3ware/Sas/Megasas/Adaptec etc.

2. Software Raid : Its managed by/throgh OS.

Now, how to manage software raids.

In this article we will learn about points,

1. Check existing software RAID configuration.
2. How to create a new RAID device.
3. Replacing a faulty device.
4. How to add device existing array.
5. Deactivating and removing an existing RAID device.

1. cat /proc/mdstat : All presently active RAID devices are stored in the /proc/mdstat file. With this command we can check our existing RAID type. It will show the list of devices.

Manage your software RAIDs, Hostripples Web Hosting

2. mdadm –query /dev/md2 : To see more informaiton about the RAID device. To display more detailed information, use the following command,
# mdadm –detail /dev/md2

Manage your software RAIDs, Hostripples Web Hosting

3. Steps to create new software raid device.

Make sure that your server is having two unused disk drives available,
# mdadm –create /dev/md2 –level=1 –raid-devices=1 /dev/sdc1 /dev/sdd1

4. Replacing a faulty device. To do so, first mark the /dev/sdb1 device as faulty:

# mdadm /dev/md2 –fail /dev/sdb1

Then remove it from the RAID device:

# mdadm /dev/md2 –remove /dev/sdb1

As soon as the hardware is replaced, you can add the device back to the array by using the following command:

# mdadm /dev/md2 –add /dev/sdb1

5. Extending a RAID Device

# mdadm /dev/md2 –add /dev/sdc1
# mdadm –grow /dev/md2 –raid-devices=2

6. Removing a RAID Device first deactivate it by running the following command as

#mdadm –stop raid_device
#mdadm –remove raid_device

7. Removing a RAID device

# mdadm –detail /dev/md2

First stop it by typing the following at a shell prompt before removing it

# mdadm –stop /dev/md2

After that you can remove it using command

# mdadm –remove /dev/md3