Re: Preparing for zfs filesystem

["Robert G. (Doc) Savage" <dsavage@peaknet.net>]

On Sat, 2013-06-15 at 22:10 -0500, Robert G. (Doc) Savage wrote:
> Steve answered my question by saying there may be array info still
> written in the initrd.
> 
> Now, will someone please tell me the syntax for zeroing the superblocks?
> The *!@#$? mdadm man page says to use --zero-superblock, but it doesn't
> give any hint or example of how it's used:
> 
> # mdadm --zero-superblock /dev/sdb
> mdadm: Couldn't open /dev/sdb for write - not zeroing
> 
> # mdadm --force --zero-superblock /dev/sdb
> mdadm: --force does not set the mode, and so cannot be the first option.
> 
> # mdadm misc --force --zero-superblock /dev/sdb
> mdadm: --force does not set the mode, and so cannot be the first option.
> 
> # mdadm misc --zero-superblock --force /dev/sdb
> mdadm: No action given for misc in --misc mode
>        Action options must come before device names
> 
> # mdadm --zero-superblock --force misc /dev/sdb
> mdadm: Couldn't open misc for write - not zeroing
> mdadm: Unrecognised md component device - /dev/sdb
> 
> I need to zero /dev/sdb thru /dev/sdj.

Failing to get any response, I'm falling back to my old standby: dd:

# dd if=/dev/zero of=/dev/sdb bs=1M

I have nine xterm windows open running this for /dev/sdb thru /dev/sdj.
Not surprisingly, this is a H-U-G-E i/o load on the system. top says the
load factor is ~30. For an 8-core system with 32GB of RAM, it's
positively *groaning* under that load. I have no idea how long it will
take.

--Doc


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