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Topic # 189430 29-Dec-2015 19:29
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I wasn't feeling confident enough to rebuild my degraded RAID 10 array (lost one of my four 2TB drive) so I decided to remake the array from scratch (using Webmin, a web based administration GUI for Ubuntu server). All was going well until it came time to create a file system when what I assume is some sort of issue due to previous configuration halted the process. Something to do with the GPT headers.

I think the best thing to do is to try and restore the drives to their default state and get rid of any trash data that might be screwing the process over.

Question time: can anyone suggest the best way for me to blank these 4 Seagate HDD's so I can throw on GPT partition tables and recreate my RAID array?

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gzt

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  Reply # 1458702 29-Dec-2015 19:46
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Gparted would be a quick fix tool for this.

gzt

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  Reply # 1458703 29-Dec-2015 19:58
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Err... Maybe gdisk. It comes with gparted.

This explains some potential issues:

http://www.rodsbooks.com/gdisk/wipegpt.html


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  Reply # 1458708 29-Dec-2015 20:26
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DBAN

Just let it run to 2% should be sufficient and it should run on all selected disks simultaneously.




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  Reply # 1458718 29-Dec-2015 20:47
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+1 for DBAN




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  Reply # 1458776 29-Dec-2015 22:03
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Thanks for the advice guys. Am I right in thinking that by Nuking with DBAN is essentially blanking the disk (no partition tables at all) and I'd have to create the GPT tables again in gdisk... but gdisk might be able repair/replace the GPT tables on its lonesome without having to wipe the disk?

 

If I'm right, is it worthwhile to nuke anyway? Will it reduce the chances that MDADM might freak out?

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  Reply # 1458799 29-Dec-2015 22:57
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If you have nothing to lose nuking is always the simplest option.

Gdisk has many option for rebuilding.

My recollection is Gparted GUI can do close to the same thing, eg; rebuilding gpt from existing partition knowledge. It has been a while since I used it. At that time the docs were not great and functionality was way ahead of them with options available in GUI but not in docs. I always found it to be really robust and generally does the right thing automatically which is/was rare in the linux world ; ).

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  Reply # 1458845 30-Dec-2015 07:22
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What's the point of having RAID if you don't use it when something goes wrong? Of course you need a backup (RAID is not a backup, and a mirror is not a backup), so what harm would a rebuild have been? If it failed you just restore from backup.




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  Reply # 1458882 30-Dec-2015 09:19
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I'd just use "dd" ... "dd if=/dev/zero of=/dev/hdx bs=1M count=1024"

Replace "/dev/hdx" with the device names for the disks, and that command will write zeros over the first 1GiB of the disk, should nuke any LVM stuff and only take a few seconds to complete.

As a matter of interest, why did you choose RAID-10 ?





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  Reply # 1459013 30-Dec-2015 13:05
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timmmay: What's the point of having RAID if you don't use it when something goes wrong? Of course you need a backup (RAID is not a backup, and a mirror is not a backup), so what harm would a rebuild have been? If it failed you just restore from backup.


I'd got everything off the array when it was in the degraded state but while I was screwing around trying to rebuild it another disk dropped out of the array; also my cron jobs and MDADM monitoring didn't do their job last time in alerting me of the initial disk failure so I decided the smartest thing to do would be to start afresh.

Mark: I'd just use "dd" ... "dd if=/dev/zero of=/dev/hdx bs=1M count=1024"

Replace "/dev/hdx" with the device names for the disks, and that command will write zeros over the first 1GiB of the disk, should nuke any LVM stuff and only take a few seconds to complete.

As a matter of interest, why did you choose RAID-10 ?


Thanks Mark, I'll try that now.

I chose RAID 10 because it seemed like a good middle-ground between RAID 5's performance and RAID 6's reliability. I get good read speeds and (if the stars align correctly) can loose a maximum of two drives. I used Near copies last time and will try Offset this time due to its read speed increase.


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  Reply # 1459458 31-Dec-2015 11:23
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The real reliability of raid, well the most common failure is down to the controller. Well, so I gather. I have been a witness to many workstation raid failures that came down to controller not handling it.



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  Reply # 1460269 2-Jan-2016 17:50
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I tried your 'dd' trick Mark but somehow it didn't work, there were still broken partition tables on the disks.
I had endless trouble trying to get the machine to boot from anything other than a Linux live CD, therefore I couldn't give DBAN a shot.

Anyway once I worked out how gdisk does its thing I managed to repair all the Partition Tables!

I have many more questions about my next moves as I try build this array, but I'll open a new thread in the Linux forum for that.

Thanks for the help!

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  Reply # 1460312 2-Jan-2016 19:21
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Incindre: I tried your 'dd' trick Mark but somehow it didn't work, there were still broken partition tables on the disks.
I had endless trouble trying to get the machine to boot from anything other than a Linux live CD, therefore I couldn't give DBAN a shot.

Anyway once I worked out how gdisk does its thing I managed to repair all the Partition Tables!

I have many more questions about my next moves as I try build this array, but I'll open a new thread in the Linux forum for that.

Thanks for the help!


Odd ... usually works for me!  Wonder if LVM puts backup copies scattered over the disk ?  Oh well sorry for the bad advise! :-)

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