----- Original Message ----- > From: "Atin Mukherjee" <amukherj@xxxxxxxxxx> > To: "CHEVALIER Pierre" <pchevalier@xxxxxxxxxxx>, gluster-users@xxxxxxxxxxx > Cc: "Pranith Kumar Karampuri" <pkarampu@xxxxxxxxxx>, "Ravishankar N" <ravishankar@xxxxxxxxxx>, "Anuradha Talur" > <atalur@xxxxxxxxxx> > Sent: Tuesday, May 17, 2016 10:02:55 PM > Subject: Re: 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. > > 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@xxxxxxxxxxx > > http://www.gluster.org/mailman/listinfo/gluster-users > > > -- Thanks, Anuradha. _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://www.gluster.org/mailman/listinfo/gluster-users
