Re: is mdadm RAID1 disk full sync

[NeilBrown <neilb@suse.de>]

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On Sat, 21 Mar 2015 19:01:54 +0800 lingli tang <tanglingli001@gmail.com>
wrote:

> I am a newbie of mdadm. I have a question but find no answer in
> document or google for last 10 days.
> 
> The question is : RAID1 made by mdadm is full sync? for example, I
> have two disk(sdb and sdc) to make RAID1 disk (/dev/md127), if I
> commit an IO to the RAID1 disk (md127), it will return back to me when
> all the two disk commit successfully      or      it will return back
> to me once just one of the disk successfully commit.

The write request will not return until it has been submitted to all, and
returned by, all working devices.

> 
> I have test with xfs and ext4 with sync option, and it seems that two
> disk have lots of commit difference after reboot the server. is that
> means mdadm return success when one of the disk is commit
> successfully?

That certainly shouldn't happen.  I would need more details of the experiment
that you performed.

NeilBrown


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