Re: [PATCH] Add '--nodes' option in GROW mode

[Guoqing Jiang <gqjiang@suse.com>]

On 03/23/2016 01:56 AM, Jes Sorensen wrote:
> zhilong <zlliu@suse.com> writes:
>> Bug description:
>> # mdadm -Cv /dev/md0 --bitmap=clustered -l1 -n2 /dev/sdd /dev/sdb
>> --nodes=6 --assume-clean
>> # mdadm --grow /dev/md0 --bitmap=none
>> # mdadm --grow /dev/md0 --bitmap=clustered
>>      -> cluster nodes would be changed to 4, here is my method to
>> resolve it.
>> # mdadm --grow /dev/md0 --bitmap=clustered --nodes=6
>>
>> Patch:
>>
>> Cluster nodes is set 4 as default when switch bitmap from
>> none to clustered under GROW mode, so add '--nodes'
>> option in GROW mode.
>>
>> Signed-off-by: Zhilong Liu <zlliu@suse.com>
>> ---
>>   mdadm.c | 1 +
>>   1 file changed, 1 insertion(+)
> Hi,
>
> I have a question about this, since I simply do not have the knowledge
> about clustering to judge this approach.
>
> If you remove the bitmap, does that 'uncluster' the array? If not,

Yes, remove the bitmap would 'uncluster' the array since leave()
will be called in kernel if switch the bitmap from 'clustered' to
'none'.

> shouldn't mdadm be fixed to not set #nodes to 4 when adding a clustered
> bitmap, if a number of cluster nodes is already present?

The nodes is set 4 by default if the 'nodes' parameter is not specified,
And it could be overwrite if re-create the clustered bitmap.

Thanks,
Guoqing