Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

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'd like to build a cheap NAS with two drives in RAID1 configuration using Linux software RAID. What are the pros and cons of having a separate system drive? My main concern is reliability of the data, I don't require high availability (failure of system drive without compromising the data on RAID would not pose a big problem).

share|improve this question
up vote 1 down vote accepted

There is no need for a whole system drive, though I recommend separating your OS and your data on different partitions.

Since Linux can boot from a RAID 1 device you have at least these options:

  1. Make a single RAID/mda device of all disks. Create a separate partitions for /, /tmp, /var, /usr and /home (aka the normal way you set up a Linux installation). Put all data on /home.
  2. Create separate RAID volumes for each and every partition. Advantage: RAID can break down for one of those but leave the rest intact. Disadvantage: more complex than a single mda device.
  3. Create a plain simple non RAID device for the OS (easiest to recover in case of disasters). Optionally copy all of that to the second drive as a backup/rescue boot. Use the rest of the disk for a RAID 1'ed /home. (E.g like this:)
    Disk 1: /, /usr, /tmp, /var , RAIDed /home
    Disk 2: (backup (dd'ed?) /, /usr, /tmp, /var , RAIDed /home

    Downside of this is that the system is not part of the RAID array, which may give poorer performance.


Better performance compared to [part of] 1 drive OS, most of 2 drives for data.

Not compared to 2 drives RAID data and an extra drive for the OS.
(Then again, with 3 drives you could use RAID 1 over 3 drives).

share|improve this answer

I recommend a separate system drive because of the following points

  • separation of system and data
  • easier to move to different hardware
  • easy and small backup of the system drive
  • better performance (not for the system but to access the data)
share|improve this answer

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.