Setting up RAID 1 on an existing CentOS


Hi Friends and Linux Expert,

Can somebody please help me how to setup raid1 on existing centOS?
I understand the concept and installation of RAID 1 software for other drives like ex. sdb and sdc but how about if i want to create a raid 1 for existing running device like sda and pair to sdb.

Hope somebody will bother to answer my newly topic.

Thank you in advance.




Follow the below link for configuring RAID 1


it wont work if you follow the link using your installed running linux on sda and pair by new device sdb


have you tried it…? why it don’t work…? can you plz explain to me, it will work try once and let us know it is working or not


it wont work, first the current sda has 2 different size which sda1 sda2 and you need to resize your sdb into the same size of what you have on sda1 and sda2.
second how you make it sdb as bootable as well if sda1 will fail
third if you use the instruction it will say your sda is currently busy

hope it make sense.


For configuring RAID both the partitions should be identical, you have to create the partition (for ex: sdb1) on sdb same like as sda2.

If sda fails or corrupted then obviously server doesn’t come up but still data is there on sdb1

if you want to make sdb as bootable you have to configure raid during the time of installing o.s like

sda1+sdb1 for boot

sda2+sdb2 for / (root)

for better info google it


ur answer is out of the topic now, what i am questioning is how to raid1 when you have existing drive that is running not that you are in time of installing the O.S. of course its a right answer that you need to raid when you are in time of installing but how about after you install an OS then you will configure a software raid1 including sda


I alrdy answered for your qes go through the below link according to my knowledge this is only the option for configuring RIDE on existing server if you found any article otherthan this let us know


Hi raghuu, i think you didn’t get what i am asking for this topic. The idea on the link you have given is very simple because its using sdb and sdc which the drives are separate from the drives of sda which the installed OS.
Anyway thanks for trying but supposedly that’s not the right answer as I have done that and not working for using the installed OS drive.