LinuxQuestions.org
LinuxAnswers - the LQ Linux tutorial section.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Hardware
User Name
Password
Linux - Hardware This forum is for Hardware issues.
Having trouble installing a piece of hardware? Want to know if that peripheral is compatible with Linux?

Notices

Reply
 
Search this Thread
Old 04-29-2008, 11:01 AM   #1
dangerousdave
Member
 
Registered: Feb 2005
Distribution: Ubuntu 8.04
Posts: 100

Rep: Reputation: 15
What's the score with Fake RAID5?


Hey. This relates to a post I made in the Newbie forum (http://www.linuxquestions.org/questi...lation-638103/), but I've refined the problem a little more now.

I have a SATA RAID5 array set up via my motherboard (Gigabyte nForce 570). After some reading it seems that the linux kernel is either bugged or simply doesn't support 'Fake RAID5'... At least that's from what I've read on the web for older versions. I'm running Ubuntu 8.04 right now.

The individual drives and the RAID controller are detected in the gnome Device Manager, but cannot be mounted.

Soo, does anyone know what the deal is with Fake RAID5 and linux, specifically Ubuntu? and if there is a simple workaround? I've read that a recompilation of the kernel may be required, if so, has anyone got any good links to tutorials on recompiling to enable Fake RAID5?

Cheers,
 
Old 04-29-2008, 01:26 PM   #2
farslayer
Guru
 
Registered: Oct 2005
Location: Willoughby, Ohio
Distribution: linuxdebian
Posts: 7,231
Blog Entries: 5

Rep: Reputation: 189Reputation: 189
if it's a fake RAID (host CPU based) controller on the motherboard, you are better of just using the software RAID in Linux. Fake RAID won't do anything for you in terms of performance and will probably perform worse than a Linux software RAID (md) setup.

If it's a true hardware based RAID you want, then look at the 3Ware RAID controllers, they have excellent Linux support imho.

You may also want to view the Fake RAID (FRAID) sucks even more at RAID-5 article... and yes it sucks in both Linux and Windows, a shortcoming of the technology and resource usage of the scheme not the OS..
 
Old 04-29-2008, 02:01 PM   #3
dangerousdave
Member
 
Registered: Feb 2005
Distribution: Ubuntu 8.04
Posts: 100

Original Poster
Rep: Reputation: 15
Cheers for the reply.

Unfortunately I have a lot of data on my RAID drive, which is also used for dual booting to Vista, so reformatting it isn't an option... especailly as it's a TB of data on there!

Soo, whats the score on getting it to work as is... anyone? please?
 
Old 04-29-2008, 02:27 PM   #4
lazlow
Senior Member
 
Registered: Jan 2006
Posts: 4,362

Rep: Reputation: 171Reputation: 171
Basically you cannot. Fakeraid uses OS drivers to do most of the raid work (by the cpu). These drivers are tied tightly to the OS. As the hardware vendors are not suppling drivers or the specifications to make drivers we are pretty much SOL. Even if they would provide the specifications it would be virtually impossible to make a driver that would allow the use of the array from both OSs(for use on one OS would be hard enough).

For true hardware raid the OS will see just the array and not the actual drives (for the most part). The hardware on the card handles all the delicate operations (whereas the cpu does this on fakeraid). So the drivers for hardware raid are relatively simple.
 
Old 04-29-2008, 02:51 PM   #5
dangerousdave
Member
 
Registered: Feb 2005
Distribution: Ubuntu 8.04
Posts: 100

Original Poster
Rep: Reputation: 15
Hmm. OK, I might have my wires crossed here. To set up my RAID I do it via the BIOS. Does this mean it's not FakeRAID that I have and instead something else? I mean, I boot up off the RAID array, so the OS has no knowledge of the array at that point?

Confused. I don't even know what type of RAID array I have now!
 
Old 04-29-2008, 05:35 PM   #6
mostlyharmless
Senior Member
 
Registered: Jan 2008
Distribution: Slackware 14.1 (multilib) with kernel 3.13.2
Posts: 1,487
Blog Entries: 11

Rep: Reputation: 154Reputation: 154
got dmraid?

It doesn't mean it isn't Fake RAID. All it means is that the OS (Vista I presume) has knowledge of it using a device driver for the CPU to do the RAID work.

Haven't tried it with RAID-5 and Vista myself, but grub and dmraid can access fake-raid from the bios and can be patched for Windows LDM in XP. There's a wiki for fake-raid under Ubuntu. You'll need an initrd (or initramfs) to activate the raid using dmraid.

But you're right, it's not supported "out of the box" for any recent distro I've tried.

Can't disagree with anything anyone else has said about whether it's a good idea - there are definitely better RAID or backup or data integrity solutions.

One problem is that there is a lot of old information out there; I would be careful that you're dealing with information that relates to recent 2.6 kernels and initramfs (not initrd, though slackware's initrd IS an initramfs) I've included a bunch of links I looked through in getting this to work. However, *this* forum usually has the best information.


https://help.ubuntu.com/community/FakeRaidHowto‏
https://www.linuxquestions.org/quest...n-e-sli-and-sl
http://grub-ldm.sourceforge.net/http...1_archive.html http://home.san.rr.com/johninsd/pub/linux/lilo/ http://it.slashdot.org/article.pl?sid=06/10/16/1935206
http://linux.die.net/man/8/dmraid‏
http://gentoo-wiki.com/HOWTO_Gentoo_..._Software_RAID http://gentoo-wiki.com/HOWTO_Migrate_To_RAID http://gentoo-wiki.com/HOWTO_Install...D_using_dmraid http://en.opensuse.org/Bugs/grub http://forums.gentoo.org/viewtopic.php?p=2053048 --
http://www.gelato.unsw.edu.au/lxr/so...ion/initrd.txt
http://fxr.watson.org/fxr/source/Doc...v=linux-2.4.22
http://splashy.alioth.debian.org/wiki/
http://splashy.alioth.debian.org/wiki/slackware
http://fixunix.com/slackware/259181-...t-execute.html
http://www.flaterco.com/kb/slackware.html
http://www.linuxquestions.org/questi...642/page2.html

Hope it helps, happy reading, backup first if at all possible!
 
Old 05-06-2008, 08:15 AM   #7
dangerousdave
Member
 
Registered: Feb 2005
Distribution: Ubuntu 8.04
Posts: 100

Original Poster
Rep: Reputation: 15
Thanks for all the help. Just a quick update on this...

Turns out that Fake RAID 4/5/6 via dmraid is bugged in the latest kernel - a regression to an earlier bug - but there is a simple fix that has just been posted:

https://bugs.launchpad.net/ubuntu/+s...ux/+bug/220493

Sorted my problem out no worries.
 
  


Reply

Tags
raid


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Newbie lookin' to score boygenuis LinuxQuestions.org Member Intro 3 10-27-2007 10:32 AM
Credit score KenMarshall General 1 04-08-2007 12:39 PM
repairing credit score maybbach General 4 11-15-2004 07:16 AM
What license should SCORE use? flamesrock Linux - Software 2 02-08-2004 09:29 PM
Debian? Whats the score? KiLLaWaBBiT Linux - Distributions 10 04-06-2003 02:30 PM


All times are GMT -5. The time now is 03:36 AM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration