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Old 02-20-2011, 02:21 AM   #1
NewAgeRetroHippie
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Unhappy Weird problem with software raid-5 mdadm


My only goal is to have a raid-5 that auto-assembles and auto-mounts.

Hardware: 4*2TB sata (raid disks), 1*500GB IDE (OS disk), 1*DVD IDE
all plugged direct into the motherboard (nForce 750i SLI).

Starting partitions on the raid disks: gpt ext4


The problem occurs when I restart my comp after building it for the first time. I am able to see it assemble, I am able to partition it, I even mounted it... Once. This is the second time I've built it so I have watched everything that happened.
I don't know if this has anything to do with my problem, but when I created the raid my drive designations were: sda - 500GB(OS), sd[bcde] - 2TB(raid). When I restarted: sd[abcd] - 2TB(raid), sde - 500GB(OS).

Here is what I got when I tried to assemble the raid:
newageretrohippie@Hippie-Media:~$ sudo mdadm --assemble --scan
[sudo] password for newageretrohippie:
mdadm: /dev/md/0 assembled from 2 drives - not enough to start the array.
mdadm: No arrays found in config file or automatically
newageretrohippie@Hippie-Media:~$ sudo mdadm --assemble /dev/md0 --uuid=618e35ea-b9f8-0614-bf63-62629b301141
mdadm: /dev/md0 assembled from 2 drives - not enough to start the array.

Do I have to stop the raid when I restart? Do I have to change mdadm.conf?


I originally tried it through the Disk Utility UI to no avail. I would build it, it would reconstruct or whatever then if I reopened Disk Utility it would say 'Warning: The partition is misaligned by 1031168 bytes. This may result in very poor performance. Repartitioning is suggested.'. I repartitioned it and got the exact same error.

I would love to be able to have it working in Disk Utility (I prefer UI's to command line).

Help please - I've had these drives for months now, unable to use them.
 
Old 02-20-2011, 07:27 PM   #2
Jerre Cope
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What distribution are you using? You shouldn't need mdadm.conf anymore. mdadm can pull it off the drives. Have you set the partitions of the RAID to "fd"

Should be something like:

mdadm -Cv /dev/md0 /dev/sdb /dev/sdc /dev/sdc /dev/sde --level=5 --raid-devices=4


plus whatever other arguments you prefer.
 
Old 02-21-2011, 01:31 AM   #3
NewAgeRetroHippie
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I'm not sure what it means to set partitions to "fd"..
I would just do 'sudo mdadm -create /dev/md0 --level=5 --raid-devices=4 /dev/sd[bcde] -chunk=1024'
 
Old 02-21-2011, 08:13 AM   #4
Jerre Cope
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Registered: Oct 2003
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When partitioning the drives with fdisk or gpartd, etc, instead of setting them to FAT, or EXT2, or whatever, set them to Linux Raid, which I believe is code "fd".

After you have the raid setup, you mkfs the type file system you want on it the /dev/md0.

You may find it helpful to

cat /proc/mdstat

to watch the rebuild happen after you initially create the drive.

You can, of course, start using the drives right away, but if you are loading an bootable os on them, confusing things can happen if you don't give it a good head start on building.
 
  


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