[Gluster-users] Upgrade Gluster 3.7 to 3.12 and add 3rd replica [howto/help]

[Martin Toth]

Hello all fellow GlusterFriends,

I would like you to comment / correct my upgrade procedure steps on replica 2 volume of 3.7.x gluster.
Than I would like to change replica 2 to replica 3 in order to correct quorum issue that Infrastructure currently has.

Infrastructure setup:
- all clients running on same nodes as servers (FUSE mounts)
- under gluster there is ZFS pool running as raidz2 with SSD ZLOG/ZIL cache
- all two hypervisor running as GlusterFS nodes and also Qemu compute nodes (Ubuntu 16.04 LTS)
- we are running Qemu VMs that accesses VMs disks via gfapi (Opennebula)
- we currently run : 1x2 , Type: Replicate volume

Current Versions :
glusterfs-* [package] 3.7.6-1ubuntu1
qemu-*		[package] 2.5+dfsg-5ubuntu10.2glusterfs3.7.14xenial1

What we need : (New versions)
- upgrade GlusterFS to 3.12 LTM version (Ubuntu 16.06 LTS packages are EOL - see https://www.gluster.org/community/release-schedule/ <https://www.gluster.org/community/release-schedule/>)
	- I want to use https://launchpad.net/~gluster/+archive/ubuntu/glusterfs-3.12 <https://launchpad.net/~gluster/+archive/ubuntu/glusterfs-3.12> as package repository for 3.12
- upgrade Qemu (with build-in support for libgfapi) - https://launchpad.net/~monotek/+archive/ubuntu/qemu-glusterfs-3.12 <https://launchpad.net/~monotek/+archive/ubuntu/qemu-glusterfs-3.12>
	- (sadly Ubuntu has packages build without libgfapi support)
- add third node to replica setup of volume (this is probably most dangerous operation)

Backup Phase
- backup "NFS storage” - raw DATA that runs on VMs
- stop all running VMs
- backup all running VMs (Qcow2 images) outside of gluster

Upgrading Gluster Phase
- killall glusterfs glusterfsd glusterd (on every server)
	(this should stop all gluster services - server and client as it runs on same nodes)
- install new Gluster Server and Client packages from repository mentioned upper (on every server) 
- install new Monotek's qemu glusterfs package with gfapi enabled support (on every server) 
- /etc/init.d/glusterfs-server start (on every server)
- /etc/init.d/glusterfs-server status - verify that all runs ok (on every server)
	- check :
		- gluster volume info
		- gluster volume status
		- check gluster FUSE clients, if mounts working as expected
- test if various VMs are able tu boot and run as expected (if libgfapi works in Qemu)
- reboot all nodes - do system upgrade of packages
- test and check again

Adding third node to replica 2 setup (replica 2 => replica 3)
(volumes will be mounted and up after upgrade and we tested VMs are able to be served with libgfapi = upgrade of gluster sucessfuly completed)
(next we extend replica 2 to replica 3 while volumes are mounted but no data is touched = no running VMs, only glusterfs servers and clients on nodes)
- issue command : gluster volume add-brick volume replica 3 node3.san:/tank/gluster/brick1 (on new single node - node3)
	so we change : 
		Bricks:
			Brick1: node1.san:/tank/gluster/brick1
			Brick2: node2.san:/tank/gluster/brick1
	to :
			Bricks:
			Brick1: node1.san:/tank/gluster/brick1
			Brick2: node2.san:/tank/gluster/brick1
			Brick3: node3.san:/tank/gluster/brick1
- check gluster status
- (is rebalance / heal required here ?)
- start all VMs and start celebration :)

My Questions
- is heal and rebalance necessary in order to upgrade replica 2 to replica 3 ?
- is this upgrade procedure OK ? What more/else should I do in order to do this upgrade correctly ?

Many thanks to all for support. Hope my little preparation howto will help others to solve same situation.

Best Regards,
Martin
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