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Re: Buster: problem changing partition size on a RAID 5 array

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Le 14/08/2017 à 06:32, Gary Dale a écrit :
> 
> Disk /dev/md1: 39068861440 sectors, 18.2 TiB
> Logical sector size: 512 bytes
> Disk identifier (GUID): EFF29D11-D982-4933-9B57-B836591DEF02
> Partition table holds up to 128 entries
> First usable sector is 34, last usable sector is 31255089118
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
You created a GPT partition table on the md array. When the table is 
created, the first and last usable sector numbers (depending on the 
device size at creation time) are recorded in the GPT header and define 
the total available space. The reason is because before the first 
available sector and after the last available sector are the two copies 
of the partition table. So changing the device size is not enough : you 
need to move the secondary partition table at the new end and adjust the 
last usable sector number.

> Neither fdisk nor gdisk let me create a partition larger than the 
> existing one. Nor do they let me create a new partition anywhere except 
> in the first 2047 sectors.

Because they rely on the GPT header to determine the available space.
With gdisk you could have used the "v" command to verify the disk and 
adjust the partition table to the new size. I don't know if fdisk can do 
it too.

> I'm not sure what the problem is that gparted was able to see but fdisk 
> and gdisk couldn't and whether this is a bug in mdadm or something else, 
> but I thought I should report it somewhere.

In the first place, the bug was to create a partition table on an md 
array. Almost nobody does this and I can see no value in doing it. It is 
useless. If you want to use the whole array as a single volume, don't 
partition it. If you want to create multiple volumes, use LVM as most 
people still do even after md arrays could be partitioned. It is much 
more flexible than partitions.

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Thread

Buster: problem changing partition size on a RAID 5 array Gary Dale <garydale@torfree.net> - 2017-08-14 06:40 +0200
  Re: Buster: problem changing partition size on a RAID 5 array Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-08-14 20:00 +0200
    Re: Buster: problem changing partition size on a RAID 5 array Gary Dale <garydale@torfree.net> - 2017-08-15 21:50 +0200
      Re: Buster: problem changing partition size on a RAID 5 array Nicholas Geovanis <nickgeovanis@gmail.com> - 2017-08-16 19:50 +0200
        Re: Buster: problem changing partition size on a RAID 5 array Gary Dale <garydale@torfree.net> - 2017-08-16 23:20 +0200
      Re: Buster: problem changing partition size on a RAID 5 array Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-08-20 16:10 +0200
        Re: Buster: problem changing partition size on a RAID 5 array Gary Dale <garydale@torfree.net> - 2017-08-21 21:00 +0200
  Re: Buster: problem changing partition size on a RAID 5 array Jimmy Johnson <field.engineer@gmail.com> - 2017-08-17 19:50 +0200

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