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Re: RAID 0+1 (Problem)



> ECJ wrote:
>
>>Hello All,
>>
>>I followed the steps in the link below but my RAID 10 array had a problem
>>after a reboot.
>>What I did was:
>>- constructed 2 RAID0s (3x73GB each)
>>- combined these 2 into a RAID1
>>- mkfs.ext3 /dev/md45 (the name of my RAID10 array)
>>- mounted it on /data
>>
>>All seemed ok. It shows on /proc/mdstat. Can write to the partition where
>>I mounted it. But after a reboot, I got errors re this new RAID device
>> and
>>was  prompted for the root password to enter repair mode.
>>Is there something I am missing here?
>>
>>
>>
> Did some tests, and was able to replicate your problem so hopefully this
> will work on your system.
>
> First, make sure the  OS can start the RAID-0's. If it can, see if you
> can start the RAID10 with:
> mdadm -As /dev/md45
>
> If you get something like:
> mdadm: no devices found for /dev/md45
>
> Then the problem is your mdadm.conf file. In that case, run:
> mdadm --examine --scan /dev/md4 /dev/md5 >> /etc/mdadm.conf
>
> And for some reason, it didn't like the devices= field on my system, so
> get rid of those and replace it with a "DEVICE partitions" line at the
> very top of the file.
>
> If you can then do the mdadm -As command, you should be good to go.
>
> And definitely talk to your boss about WHY he wants mirrored stripes.
> If its for 'performance reasons' offer to bench the two and that should
> show him that any performance difference would be statistically
> insignificant and not worth the loss of redundancy. Having numbers to
> back up your case may help.
>
> Hope this helps,
>
> Daniel
>
I scrapped the mirrored stripe and switched to striped mirror. What the
heck. So I then created 3 mirrors and joined them together. Everything
went ok.
- 3 RAID1s - /dev/md4 /dev/md5 /dev/md6
- combined them to RAID 0 - /dev/md10
- Did mkfs.ext3 /dev/md10
- Added md10 to /etc/mdadm.conf. Doing 'mdadm --examine --scan
--config=/etc/mdadm.conf' shows all my RAID arrays correctly.

Now I tried stopping /dev/md10 then restarted it with 'mdadm -As
/dev/md10' but then it gives me an error that 'no devices found for
/dev/md10.' If I do 'mdadm --examine --scan --config=/etc/mdadm.conf,'
/dev/md10 shows up. Any more suggestions? I've given myself until today to
make this work, or else I'm gonna go for RAID5.

Thanks to all.
Edward






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