Le 19/05/2016 12:06, Anuradha Talur a écrit :
----- Original Message -----
From: "Atin Mukherjee" <amukh...@redhat.com>
To: "CHEVALIER Pierre" <pcheval...@imajing.org>, gluster-users@gluster.org
Cc: "Pranith Kumar Karampuri" <pkara...@redhat.com>, "Ravishankar N"
<ravishan...@redhat.com>, "Anuradha Talur"
<ata...@redhat.com>
Sent: Tuesday, May 17, 2016 10:02:55 PM
Subject: Re: [Gluster-users] 2 nodes volume with existing data
On 05/17/2016 01:59 PM, CHEVALIER Pierre wrote:
Hi everyone,
I have found a similar question in the ML but didn't find the answer I
wanted.
My situation is the following :
We have 2 existing data storage unit with 72TB each, with 10TB left.
Currently these storage unit are synced using rsync periodically. We
want to tansform these 2 nodes into glusterfs bricks without loosing any
data or deleting a node.
I was thinking setting up the 2 nodes with glusterfs in replica this way :
1) Rsync server1/brick1 and server2/brick2 content
2) Create the gluster replica and start :
gluster volume create volume1 replica 2 transport tcp server1:/brick1
server2:/brick1
gluster volume start volume1
Gluster heavily depends on extended attributes for its business logic
and hence configuring a brick with existing data means that the extended
attributes would not be set for these files and hence this may not work
as per the expectation.
Given that you have a restriction using another brick, I'd suggest you
to do the following:
1. Delete all the contents of server2/brick as this is a secondary copy
2. Create a plain distributed volume in server2 with server2/brick1
2. Start the volume
3. Mount the volume and then do copy the content from server1/brick1 to
the mount point.
4. Probe server2 into the cluster
5. Perform an add-brick with server1/brick by gluster volume add-brick
<volname> replica 2 <brick name> (Again make sure the content is deleted
first)
6. This should trigger the self heal
As of now converting a plain distribute volume to distribute replicate is not
going to
automatically heal the files. (We are working on a solution for this.)
If you really want to go ahead with this method then I'd recommend you to do
the following :
1) Stop I/O on your volume.
2) Add the new brick.
3) Stop and start your gluster volume
4) Trigger lookup on the files from mount point by doing find . | xargs stat on
the mount point.
This should trigger heals on the new brick.
Hi,
OK this is good news, I wanted to avoid to have no backup of the content.
So after that I mount the new volume as gluster fs and can start I/O on
it ?
Thanks for these informations.
However since the data volume is very high, self heal can take a longer
time to sync and finish.
Also with a two node setup prevention of split brains is not guaranteed.
An arbiter volume or a 3 way replica would be the solution to tackle
this problem.
Since I am not an AFR expert, I'd like to get a sign off from AFR team
(In cc) before you try this out.
~Atin
Then, should I run a healing process, or stat each files in order to
self heal ?
What happens if there is a slight difference between the 2 nodes,
mathematically if :
server1/brick1= server2/brick1+delta
Will the delta part impact server1, or will it be lost ?
Maybe I worry for nothing, but as these 2 nodes host important data, I
wanted to make sure that eveything is OK.
Thanks for your help !
--
Pierre CHEVALIER
_______________________________________________
Gluster-users mailing list
Gluster-users@gluster.org
http://www.gluster.org/mailman/listinfo/gluster-users
--
Pierre CHEVALIER
_______________________________________________
Gluster-users mailing list
Gluster-users@gluster.org
http://www.gluster.org/mailman/listinfo/gluster-users
