Re: Confusion with setting up new RAID6 with mdadm

[Zoltan Szecsei <zoltans@geograph.co.za>]

On 2010-11-15 14:47, Michal Soltys wrote:
> On 15.11.2010 13:27, Zoltan Szecsei wrote:
>> On 2010-11-14 18:48, Mikael Abrahamsson wrote:
>>>
>>>> *What is the correct fdisk or parted method get rid of the DOS & GPT
>>>> flags, and create a correctly aligned partition, and should this be a
>>>> 0xda partiton (& then I use metatdata 1.2 for mdadm)?
>>>
>>> I just "dd if=/dev/zero of=/dev/sdX bs=1024000 count=1" to zero the
>>> first megabyte of the drive to get rid of the partition table (you get
>>> rid of the v1.2 metadata at the same time actually). Then you know for
>>> sure you're correctly aligned as well as md is 4k aligned.
>> I did this on all 8 drives (/dev/sd[a-h])
>> root@gs0:/etc# dd if=/dev/zero of=/dev/sdb bs=1024000 count=1
>> 1+0 records in
>> 1+0 records out
>> 1024000 bytes (1.0 MB) copied, 0.0103209 s, 99.2 MB/s
>> root@gs0:/etc# dd if=/dev/zero of=/dev/sdc bs=1024000 count=1
>>
>> But the GPT id has not disappeared.
>
> You might want to do blockdev --rereadpt /dev/sd[a-h] to make sure 
> kernel registers new situation (or do the same with sfdisk -R)
>
> Also, GPT stores backup partition table + gpt header at the end of the 
> disk. Kernel might be clever enough to rely on it if you destroy the 
> data at the beginning of the disk.
>

OK, just done this on all 8 drives:
root@gs0:/sys/block# dd if=/dev/zero of=/dev/sdb bs=512 seek=3907029166
dd: writing `/dev/sdb': No space left on device
3+0 records in
2+0 records out
1024 bytes (1.0 kB) copied, 0.000913281 s, 1.1 MB/s
root@gs0:/sys/block#


fdisk -lu produces the results below - so presumably the drives now 
clean & ready for mdadm?

BTW: I've just downloaded and compiled the latest mdadm too:
root@gs0:/sys/block# mdadm -V
mdadm - v3.1.4 - 31st August 2010
root@gs0:/sys/block#


Thanks for your (collective) helps...
Zoltan



root@gs0:/sys/block# fdisk -lu

Disk /dev/sda: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sda doesn't contain a valid partition table

Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/sdc: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdc doesn't contain a valid partition table

Disk /dev/sdd: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdd doesn't contain a valid partition table

Disk /dev/sde: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sde doesn't contain a valid partition table

Disk /dev/sdf: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdf doesn't contain a valid partition table

Disk /dev/sdg: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdg doesn't contain a valid partition table

Disk /dev/sdh: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdh doesn't contain a valid partition table

Disk /dev/sdi: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000e30c7

    Device Boot      Start         End      Blocks   Id  System
/dev/sdi1   *        2048      391167      194560   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sdi2          393214   976771071   488188929    5  Extended
/dev/sdi5          393216    98047999    48827392   83  Linux
/dev/sdi6        98050048   110047231     5998592   82  Linux swap / Solaris
/dev/sdi7       110049280   976771071   433360896   83  Linux
root@gs0:/sys/block#







-- 

===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
P.O. Box 7, Muizenberg 7950, South Africa.

65 Main Road, Muizenberg 7945
Western Cape, South Africa.

34° 6'16.35"S 18°28'5.62"E

Tel: +27-21-7884897  Mobile: +27-83-6004028
Fax: +27-86-6115323     www.geograph.co.za
===========================================



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