RAID-1, Part 1

What it is, when to use it, how to make a RAID-1 device for an ext2 partition.

The Software-RAID HOWTO

"Kernel Korner: The Linux RAID-1, 4, 5 Code", Linux Journal, December 1997.

Usenet; one of the archives is The following search queries may help to get you started: +RAID1, +failed-disk +linux, +RAID1 +swap +linux and +linux +RAID +superblock.

If you're curious about the RAID superblock, you can find a description in the mdctl-0.5 source code. Take a look at the file md_p.h. You also can take a look at the kernel mddriver source code files including /usr/src/linux/drivers/md/md.c.


Thanks to those who developed the Linux RAID code (see drivers/md/md.c for names), Jakob Østergaard for the "The Software-RAID HOWTO", the Usenet correspondents and Niel Brown for mdctl.

Joe Edwards, PE, PhD wrote his first useful program using FORTRAN on an IBM 370 almost 30 years ago. The program performed forensic analysis of X-ray diffraction data. He started using Linux in 1995. He is the lead programmer, sysadmin and dba for the GeneTests-GeneClinics Projects at the University of Washington.

Audin Malmin is a programmer and sysadmin for the GeneTests-GeneClinics Projects at the University of Washington. His first programming experiences were on his dad's Timex Sinclair 1000. He first experimented with Linux in 1996 on his 386sx16 with 3MB of RAM.

Ron Shaker is the lead programmer on the GeneSeek Project at the University of Washington. He has worked as a sysadmin, dba and systems engineer over the past 13 years and began using UNIX in 1988.



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would be nice to also know how to uninstall

Anonymous's picture

how to take a raid-1 system and return it to two separate disks?

how to unbuild what one has built?

would be nice to see this information, as well. (it's also missing from the linux software-raid howto and other similar articles online)

Useless Mirror

Anonymous's picture

I echo the last comment. What's the use of RAID if the system still fails? I have done multiple Fedora installs attempting to RAID1 entire system. All installs go well, system runs great. When a disk is removed system hangs. When you re-boot and add the disk back it rebuilds and works fine again. It seems some pertinent information is missing from all these articles and how to's on linux RAID.

Useless. How do we mirror

Anonymous's picture

Useless. How do we mirror root then? Copy it to a temp location, unmount it and format???? In Solaris, metadevices can be created on the fly.

Chunk sizes, blocks sizes, groups?

warp9pnt9's picture

Where is the discussion on the performance effect of raid chunk size, and ext2 (ext3?) filesystem properties?

RAID clarification

Srikumar's picture

I have seen ur article
I need some clarification about software raid 1
I have installed Redhat Linux 9 using Software RAID 1
I am using only two..not giving any spares
But if one hard disk fail, i will create another hard disk with the same partions
can i concatinate the two partions as a single RAID with out formatting
And i m getting problem when i install some network drivers.
The drivers are not installing
Where might be the problem????

Try mdadm !

K M Ashraf's picture

Try the new RAID for Linux management tool 'mdadm'

Re: RAID-1, Part 1

Anonymous's picture

Good info I guess. LD