[mythtv-users] RAID: full disk or partition (was: Question re: available SATA ports and linux software RAID)

John Drescher drescherjm at gmail.com
Wed Apr 27 02:50:00 UTC 2011

On Tue, Apr 26, 2011 at 10:41 PM, John Drescher <drescherjm at gmail.com> wrote:
> On Tue, Apr 26, 2011 at 10:30 PM, Jean-Yves Avenard <jyavenard at gmail.com> wrote:
>> On 27 April 2011 12:27, John Drescher <drescherjm at gmail.com> wrote:
>>> And I meant drives that are connected. One could always reboot pulling
>>> the sata cable. Assemble whatever array then plug the drive in and
>>> zero the superblock or zero it in some other machine.
>> Will zeroing the /dev/sdd superblock write anywhere on the /dev/sdd1 partition?
>> That's my main concern..
>> Otherwise, I'll have to manually fail each disk, remove them, re-add
>> them... So I'm up for a few more days of md rebuilding (took me a week
>> already to change the 1.5TB to 2TB disks ...)
> What superblock are you using 1.2?
> You may be able to manually zap the superblock like I did in this thread:
> http://forums.gentoo.org/viewtopic-t-845757-start-0.html
> Here is the link again to the wikipedia article that talks about the
> superblock format.
> https://raid.wiki.kernel.org/index.php/RAID_superblock_formats#The_version-1_Superblock_Format

Your superblock is 0.90 from your output so you need to what I did.
"The superblock is 4K long and is written into a 64K aligned block
that starts at least 64K and less than 128K from the end of the device
(i.e. to get the address of the superblock round the size of the
device down to a multiple of 64K and then subtract 64K). The available
size of each device is the amount of space before the super block, so
between 64K and 128K is lost when a device in incorporated into an MD
array. "

Look for the magic number fc 4e 2b a9 00 in this region.



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