Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I run a Windows Server 2008 machine. It is used as a file server (File Services feature), in addition to local shares I use CrushFTP for SFTP and HTTP access to my files. I would like to convert to Linux (Ubuntu at first).

What I want is to install the OS on a single HDD (500 GB) and then have a software RAID 1 with two 2 TB HDDs. The RAID 1 volume will be used only for storing, and all programs will be installed on the OS HDD.

In what stage of this setup should I make the RAID 1 volume? I have been searching around and it seems like most guides suggests making it during the installation of the OS. Is this the best way to do it, and when I upgrade with more HDDs, will I be able to extend the volume?

share|improve this question
You can't make a RAID1 volume larger by adding more disks, that's not how RAID1 works. – jordanm Oct 15 '13 at 17:26
@jordanm You can't make a RAID1 volume larger by adding more disks, but you can make it larger by replacing the smallest disk by a larger one. – Gilles Oct 16 '13 at 1:07
I meant: is it possible to replace one of the 2TB disks with a 4TB disk, and when it is synced, replace the remaining 2TB with another 4TB and my RAID is now 4TB without losing data in the process. – Espen Oct 16 '13 at 11:58
up vote 0 down vote accepted

You need to create the RAID1 volume during installation if you want to install to a RAID1 volume. You're finding this in guides because usually, when people are asking about installation and about RAID, it's because they want to install on RAID.

Since you don't want to install on a RAID volume, you have no RAID volume to create during installation.

You need to create the RAID volume when you connect the first disk that should be in this volume to your system. This is done with the mdadm command.

The size of a RAID1 volume is the size of the smallest disk that makes up that volume. If at some point you replace the smallest disk by a larger disk, you can grow the volume to cover the disk that is now the smallest one.

share|improve this answer
Thanks for your answer :) – Espen Oct 16 '13 at 11:59

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.