Re: Confusion with setting up new RAID6 with mdadm

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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. I am going to use these drives unpartitioned, so is this a problem?

Thanks,
Zoltan

root@gs0:/etc# fdisk -lu

WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdd'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sde'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdf'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdg'! The util fdisk doesn't support GPT. Use GNU Parted.


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

WARNING: GPT (GUID Partition Table) detected on '/dev/sdh'! The util fdisk doesn't support GPT. Use GNU Parted.


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:/etc#




--

===========================================
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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