Why does md3 persist after deleting and recreating the partitions?

Why does md3 persist after deleting and recreating the partitions?

[Mark Knecht]

Hi,
   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
partitions using fdisk, and then created 5 new partitions using
sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
are the same size as the old ones and located at the same sector
addresses.

   After rebooting, but before creating the new RAID6, I still see md3:

mark@c2stable ~ $ cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
      247416933 blocks super 1.1 [3/3] [UUU]

md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
      52436096 blocks [3/3] [UUU]

md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
      52436032 blocks [3/3] [UUU]

unused devices: <none>
mark@c2stable ~ $


   What am I doing wrong or forgetting? I would like md3 to be totally
gone before I create a new md3 in it's place.

Thanks,
Mark

Re: Why does md3 persist after deleting and recreating the partitions?

[Mathias Burén]

On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
> Hi,
>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
> partitions using fdisk, and then created 5 new partitions using
> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
> are the same size as the old ones and located at the same sector
> addresses.
>
>   After rebooting, but before creating the new RAID6, I still see md3:
>
> mark@c2stable ~ $ cat /proc/mdstat
> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
>      247416933 blocks super 1.1 [3/3] [UUU]
>
> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
>      52436096 blocks [3/3] [UUU]
>
> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
>      52436032 blocks [3/3] [UUU]
>
> unused devices: <none>
> mark@c2stable ~ $
>
>
>   What am I doing wrong or forgetting? I would like md3 to be totally
> gone before I create a new md3 in it's place.
>
> Thanks,
> Mark
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Erase the superblocks? Recreating partitions doesn't (usually) affect
the data on the HDDs.

// M
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Re: Why does md3 persist after deleting and recreating the partitions?

[Mark Knecht]

On Thu, Dec 30, 2010 at 4:12 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
> On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
>> Hi,
>>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
>> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
>> partitions using fdisk, and then created 5 new partitions using
>> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
>> are the same size as the old ones and located at the same sector
>> addresses.
>>
>>   After rebooting, but before creating the new RAID6, I still see md3:
>>
>> mark@c2stable ~ $ cat /proc/mdstat
>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
>> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
>>      247416933 blocks super 1.1 [3/3] [UUU]
>>
>> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
>>      52436096 blocks [3/3] [UUU]
>>
>> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
>>      52436032 blocks [3/3] [UUU]
>>
>> unused devices: <none>
>> mark@c2stable ~ $
>>
>>
>>   What am I doing wrong or forgetting? I would like md3 to be totally
>> gone before I create a new md3 in it's place.
>>
>> Thanks,
>> Mark
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
> Erase the superblocks? Recreating partitions doesn't (usually) affect
> the data on the HDDs.
>
> // M
>

Is erasing the superblocks a mdadm operation? I've not heard of that one before.

Thanks,
Mark
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Re: Why does md3 persist after deleting and recreating the partitions?

[Mathias Burén]

On 31 December 2010 00:14, Mark Knecht <markknecht@gmail.com> wrote:
> On Thu, Dec 30, 2010 at 4:12 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
>> On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
>>> Hi,
>>>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
>>> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
>>> partitions using fdisk, and then created 5 new partitions using
>>> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
>>> are the same size as the old ones and located at the same sector
>>> addresses.
>>>
>>>   After rebooting, but before creating the new RAID6, I still see md3:
>>>
>>> mark@c2stable ~ $ cat /proc/mdstat
>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
>>> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
>>>      247416933 blocks super 1.1 [3/3] [UUU]
>>>
>>> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
>>>      52436096 blocks [3/3] [UUU]
>>>
>>> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
>>>      52436032 blocks [3/3] [UUU]
>>>
>>> unused devices: <none>
>>> mark@c2stable ~ $
>>>
>>>
>>>   What am I doing wrong or forgetting? I would like md3 to be totally
>>> gone before I create a new md3 in it's place.
>>>
>>> Thanks,
>>> Mark
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>> Erase the superblocks? Recreating partitions doesn't (usually) affect
>> the data on the HDDs.
>>
>> // M
>>
>
> Is erasing the superblocks a mdadm operation? I've not heard of that one before.
>
> Thanks,
> Mark
>

Yes, see mdadm --misc. Like:

mdadm --zero-superblock <device>

// M
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Re: Why does md3 persist after deleting and recreating the partitions?

[Mark Knecht]

On Thu, Dec 30, 2010 at 4:16 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
> On 31 December 2010 00:14, Mark Knecht <markknecht@gmail.com> wrote:
>> On Thu, Dec 30, 2010 at 4:12 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
>>> On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
>>>> Hi,
>>>>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
>>>> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
>>>> partitions using fdisk, and then created 5 new partitions using
>>>> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
>>>> are the same size as the old ones and located at the same sector
>>>> addresses.
>>>>
>>>>   After rebooting, but before creating the new RAID6, I still see md3:
>>>>
>>>> mark@c2stable ~ $ cat /proc/mdstat
>>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
>>>> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
>>>>      247416933 blocks super 1.1 [3/3] [UUU]
>>>>
>>>> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
>>>>      52436096 blocks [3/3] [UUU]
>>>>
>>>> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
>>>>      52436032 blocks [3/3] [UUU]
>>>>
>>>> unused devices: <none>
>>>> mark@c2stable ~ $
>>>>
>>>>
>>>>   What am I doing wrong or forgetting? I would like md3 to be totally
>>>> gone before I create a new md3 in it's place.
>>>>
>>>> Thanks,
>>>> Mark
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>> Erase the superblocks? Recreating partitions doesn't (usually) affect
>>> the data on the HDDs.
>>>
>>> // M
>>>
>>
>> Is erasing the superblocks a mdadm operation? I've not heard of that one before.
>>
>> Thanks,
>> Mark
>>
>
> Yes, see mdadm --misc. Like:
>
> mdadm --zero-superblock <device>
>
> // M
>

Yes, just found that.

Can I still use /dev/md3 safely even though it's no longer in
mdadm.conf? I suspect I can?

Cheers,
Mark
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Re: Why does md3 persist after deleting and recreating the partitions?

[Neil Brown]

On Thu, 30 Dec 2010 16:17:51 -0800 Mark Knecht <markknecht@gmail.com> wrote:

> On Thu, Dec 30, 2010 at 4:16 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
> > On 31 December 2010 00:14, Mark Knecht <markknecht@gmail.com> wrote:
> >> On Thu, Dec 30, 2010 at 4:12 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
> >>> On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
> >>>> Hi,
> >>>>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
> >>>> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
> >>>> partitions using fdisk, and then created 5 new partitions using
> >>>> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
> >>>> are the same size as the old ones and located at the same sector
> >>>> addresses.
> >>>>
> >>>>   After rebooting, but before creating the new RAID6, I still see md3:
> >>>>
> >>>> mark@c2stable ~ $ cat /proc/mdstat
> >>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> >>>> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
> >>>>      247416933 blocks super 1.1 [3/3] [UUU]
> >>>>
> >>>> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
> >>>>      52436096 blocks [3/3] [UUU]
> >>>>
> >>>> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
> >>>>      52436032 blocks [3/3] [UUU]
> >>>>
> >>>> unused devices: <none>
> >>>> mark@c2stable ~ $
> >>>>
> >>>>
> >>>>   What am I doing wrong or forgetting? I would like md3 to be totally
> >>>> gone before I create a new md3 in it's place.
> >>>>
> >>>> Thanks,
> >>>> Mark
> >>>> --
> >>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> >>>> the body of a message to majordomo@vger.kernel.org
> >>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>>>
> >>>
> >>> Erase the superblocks? Recreating partitions doesn't (usually) affect
> >>> the data on the HDDs.
> >>>
> >>> // M
> >>>
> >>
> >> Is erasing the superblocks a mdadm operation? I've not heard of that one before.
> >>
> >> Thanks,
> >> Mark
> >>
> >
> > Yes, see mdadm --misc. Like:
> >
> > mdadm --zero-superblock <device>
> >
> > // M
> >
> 
> Yes, just found that.
> 
> Can I still use /dev/md3 safely even though it's no longer in
> mdadm.conf? I suspect I can?

That sentence doesn't make much sense to me, so I suspect some misunderstand
is going on.  So to be explicit:

  Use
    mdadm --zero-superblock /dev/sdc3 /dev/sdb3 /dev/sda3

 to remove  from those devices any record that they are part of any md array.

Does that clarify thing sufficienty?

NeilBrown

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Re: Why does md3 persist after deleting and recreating the partitions?

[Mark Knecht]

On Thu, Dec 30, 2010 at 5:07 PM, Neil Brown <neilb@suse.de> wrote:
> On Thu, 30 Dec 2010 16:17:51 -0800 Mark Knecht <markknecht@gmail.com> wrote:
>
>> On Thu, Dec 30, 2010 at 4:16 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
>> > On 31 December 2010 00:14, Mark Knecht <markknecht@gmail.com> wrote:
>> >> On Thu, Dec 30, 2010 at 4:12 PM, Mathias Burén <mathias.buren@gmail.com> wrote:
>> >>> On 31 December 2010 00:10, Mark Knecht <markknecht@gmail.com> wrote:
>> >>>> Hi,
>> >>>>   What am I forgetting to do? I had a RAID1 using sd{a,b,c}3. I
>> >>>> stopped md3, removed the md3 line in /etc/mdadm.conf, deleted the
>> >>>> partitions using fdisk, and then created 5 new partitions using
>> >>>> sd{a,b,c,d,e}3 to get ready to do a 5 disk RAID6. The new partitions
>> >>>> are the same size as the old ones and located at the same sector
>> >>>> addresses.
>> >>>>
>> >>>>   After rebooting, but before creating the new RAID6, I still see md3:
>> >>>>
>> >>>> mark@c2stable ~ $ cat /proc/mdstat
>> >>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
>> >>>> md6 : active raid1 sdb6[1] sdc6[2] sda6[0]
>> >>>>      247416933 blocks super 1.1 [3/3] [UUU]
>> >>>>
>> >>>> md3 : active raid1 sdc3[2] sdb3[1] sda3[0]
>> >>>>      52436096 blocks [3/3] [UUU]
>> >>>>
>> >>>> md5 : active raid1 sdc5[2] sdb5[1] sda5[0]
>> >>>>      52436032 blocks [3/3] [UUU]
>> >>>>
>> >>>> unused devices: <none>
>> >>>> mark@c2stable ~ $
>> >>>>
>> >>>>
>> >>>>   What am I doing wrong or forgetting? I would like md3 to be totally
>> >>>> gone before I create a new md3 in it's place.
>> >>>>
>> >>>> Thanks,
>> >>>> Mark
>> >>>> --
>> >>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> >>>> the body of a message to majordomo@vger.kernel.org
>> >>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> >>>>
>> >>>
>> >>> Erase the superblocks? Recreating partitions doesn't (usually) affect
>> >>> the data on the HDDs.
>> >>>
>> >>> // M
>> >>>
>> >>
>> >> Is erasing the superblocks a mdadm operation? I've not heard of that one before.
>> >>
>> >> Thanks,
>> >> Mark
>> >>
>> >
>> > Yes, see mdadm --misc. Like:
>> >
>> > mdadm --zero-superblock <device>
>> >
>> > // M
>> >
>>
>> Yes, just found that.
>>
>> Can I still use /dev/md3 safely even though it's no longer in
>> mdadm.conf? I suspect I can?
>
> That sentence doesn't make much sense to me, so I suspect some misunderstand
> is going on.  So to be explicit:
>
>  Use
>    mdadm --zero-superblock /dev/sdc3 /dev/sdb3 /dev/sda3
>
>  to remove  from those devices any record that they are part of any md array.
>
> Does that clarify thing sufficienty?
>
> NeilBrown

Yes, making sure to do

mdadm -S /dev/md3

first.

/dev/md3 seems to be gone at this point. On to doing the new RAID6.
(See other thread - no one has responded to that one yet.)

Thanks again,
Mark
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