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Old 09-10-2007, 06:57 PM   #1
pnotequalsnp
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Raid 5 setup


Thank-you in advance for answering my questions.

I have 4 SATA 500GB drives and 1 SATA 150GB Raptor drive. Using mdadm, I set up raid 5 (software) using the 4 500GB drives and I installed my distribution (Ubuntu) on the 150GB drive.

I was wondering, if the 150GB OS drive fails (no redundancy), will I be able to recover the raid 5 setup or is this dependent on the current installation?

I would prefer not to be in the red if my OS drive fails and I can set up the raid 5 again after reinstalling an OS.

Thanks!
 
Old 09-10-2007, 10:55 PM   #2
cojo
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pnote,

since you are using SATA drive. Your motherboard most likely will allow you to setup raid 5. I would suggest you use hard raid instead of software raid. This will take the load of the OS and your raid set won't depend on your 150GB SATA drive.

Since, your current raid setting is on the 150GB drive and you will most likely lose the setting if you lose the 150GB drive.
 
Old 09-10-2007, 11:41 PM   #3
pnotequalsnp
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Thanks. I was hoping that I could restore the raid 5 if the 150GB failed, I guess not. The reason I do not use Hardware is that it is too expensive, I do not use the raid setup except for storage (not read/write intensive), I have more than enough CPU/memory (quad core/8GB) and the software raid was really easy to create using gparted and mdadm.

Is there a way to preserve the raid settings or conifuration so that if I reinstall the OS I can get the raid back. This seems intuitive from the clouds but the implementation on the ground may be different.

Anyone have any ideas.
 
Old 09-11-2007, 12:04 AM   #4
cojo
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pnote,

most of the new motherboard came with raid configuration for SATA. So, it shouldn't cost you anything at all. Not sure about backing up the raid setting. I will research on my test server tomorrow and get back with you.
 
Old 09-11-2007, 01:58 AM   #5
pnotequalsnp
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thank you for testing cojo, I really appreciate it. I have a mb with "raid" but it is in fact "fake raid". I read that this means it has hardware that helps in the raid process but is not in fact a raid card. My mother board is an Abit AB9 QuadGT for reference,
p not equals np
 
Old 10-18-2007, 11:55 AM   #6
eRJe
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Hi there,

I believe you can restore your raid array after reinstalling your OS drive. mdadm puts info in the superblock and not on the OS drive anymore. Keep a copy of raidtab for your own reference whenever you do need to recover your raid array. (raidtab is obsolete and only for reference anyway)

I'm far-FAR away from expert but I have been experimeting quit a lot with raid-5 over the last few weeks. I have reinstalled my OS more then once on a complete new drive and have always been able to recover my raid array.

My previous (old) raid-0 was even recognised automatically after reinstalling my OS.

Good luck!

Robbert

btw As far as I know all onboard raid controllers are fake. Also when your motherboard fails, it will be more difficult to restore the raid array.
 
Old 11-16-2007, 03:02 AM   #7
student04
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Quote:
Originally Posted by eRJe View Post
btw As far as I know all onboard raid controllers are fake. Also when your motherboard fails, it will be more difficult to restore the raid array.
Is this really true (that about being fake and harder to recover)? I recently bought a new motherboard (ASUS M2N32-SLI Deluxe) and it comes with two onboard RAID controllers. Currently I have Vista installed with a controller setup to handle RAID 5 across three identical disks. I've been doing a lot of reading about this and it seems to be that I would need to use dmraid to configure my system to allow Linux to install. If it's harder to recover with this fake raid then what's the point?

The Nvidia Control Panel claims it can rebuild the array while Vista is running when a drive is down without messing things up, though it warned that it would take its time.

Sources:
-First line of first post: gentoo-forums
-"Simon Bridge" says it won't work at all... LQ forum: here

Some other forum posts I've read have links to comparisons for performance of hardware-based raid and software-based raid. ("Simon Bridge"'s post has such a link, above).

Basically I'm looking for a reliable way to prevent data from being lost if a disk fails. I don't really have enough cash for a RAID controller, and my needs are not that great for one at the moment.

I also read GRUB doesn't work when on an onboard RAID config...?

Does anyone recommend something? I'll reinstall everything if I have to, but I really want to at least tri-boot my system with Vista on NTFS, Kubuntu on ext3 and Gentoo on reiserfs (to play with).

If it's too much of an issue i'd also be willing to go without the entire RAID setup, but if it will work without much trouble i'll keep it.

Thanks for any input!

-AM
 
  


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