I'm now also confused as to what the point of an arbiter is / what it does / why one would use it.

On Fri, Sep 1, 2017 at 11:44 AM, Jim Kusznir <jim@palousetech.com> wrote:
Thanks for the help!

Here's my gluster volume info for the data export/brick (I have 3: data, engine, and iso, but they're all configured the same):

Volume Name: data
Type: Replicate
Volume ID: e670c488-ac16-4dd1-8bd3-e43b2e42cc59
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x (2 + 1) = 3
Transport-type: tcp
Bricks:
Brick1: ovirt1.nwfiber.com:/gluster/brick2/data
Brick2: ovirt2.nwfiber.com:/gluster/brick2/data
Brick3: ovirt3.nwfiber.com:/gluster/brick2/data (arbiter)
Options Reconfigured:
performance.strict-o-direct: on
nfs.disable: on
user.cifs: off
network.ping-timeout: 30
cluster.shd-max-threads: 8
cluster.shd-wait-qlength: 10000
cluster.locking-scheme: granular
cluster.data-self-heal-algorithm: full
performance.low-prio-threads: 32
features.shard-block-size: 512MB
features.shard: on
storage.owner-gid: 36
storage.owner-uid: 36
cluster.server-quorum-type: server
cluster.quorum-type: auto
network.remote-dio: enable
cluster.eager-lock: enable
performance.stat-prefetch: off
performance.io-cache: off
performance.read-ahead: off
performance.quick-read: off
performance.readdir-ahead: on
server.allow-insecure: on
[root@ovirt1 ~]#


all 3 of my brick nodes ARE also members of the virtualization cluster (including ovirt3).  How can I convert it into a full replica instead of just an arbiter?

Thanks!
--Jim

On Fri, Sep 1, 2017 at 9:09 AM, Charles Kozler <ckozleriii@gmail.com> wrote:
@Kasturi - Looks good now. Cluster showed down for a moment but VM's stayed up in their appropriate places. Thanks!

< Anyone on this list please feel free to correct my response to Jim if its wrong> 

@ Jim - If you can share your gluster volume info / status I can confirm (to the best of my knowledge). From my understanding, If you setup the volume with something like 'gluster volume set <vol> group virt' this will configure some quorum options as well, Ex: http://i.imgur.com/Mya4N5o.png

While, yes, you are configured for arbiter node you're still losing quorum by dropping from 2 -> 1. You would need 4 node with 1 being arbiter to configure quorum which is in effect 3 writable nodes and 1 arbiter. If one gluster node drops, you still have 2 up. Although in this case, you probably wouldnt need arbiter at all

If you are configured, you can drop quorum settings and just let arbiter run since you're not using arbiter node in your VM cluster part (I believe), just storage cluster part. When using quorum, you need > 50% of the cluster being up at one time. Since you have 3 nodes with 1 arbiter, you're actually losing 1/2 which == 50 which == degraded / hindered gluster 
  
Again, this is to the best of my knowledge based on other quorum backed software....and this is what I understand from testing with gluster and ovirt thus far

On Fri, Sep 1, 2017 at 11:53 AM, Jim Kusznir <jim@palousetech.com> wrote:
Huh...Ok., how do I convert the arbitrar to full replica, then?  I was misinformed when I created this setup.  I thought the arbitrator held enough metadata that it could validate or refudiate  any one replica (kinda like the parity drive for a RAID-4 array).  I was also under the impression that one replica  + Arbitrator is enough to keep the array online and functional.

--Jim

On Fri, Sep 1, 2017 at 5:22 AM, Charles Kozler <ckozleriii@gmail.com> wrote:
@ Jim - you have only two data volumes and lost quorum. Arbitrator only stores metadata, no actual files. So yes, you were running in degraded mode so some operations were hindered.

@ Sahina - Yes, this actually worked fine for me once I did that. However, the issue I am still facing, is when I go to create a new gluster storage domain (replica 3, hyperconverged) and I tell it "Host to use" and I select that host. If I fail that host, all VMs halt. I do not recall this in 3.6 or early 4.0. This to me makes it seem like this is "pinning" a node to a volume and vice versa like you could, for instance, for a singular hyperconverged to ex: export a local disk via NFS and then mount it via ovirt domain. But of course, this has its caveats. To that end, I am using gluster replica 3, when configuring it I say "host to use: " node 1, then in the connection details I give it node1:/data. I fail node1, all VMs halt. Did I miss something?

On Fri, Sep 1, 2017 at 2:13 AM, Sahina Bose <sabose@redhat.com> wrote:
To the OP question, when you set up a gluster storage domain, you need to specify backup-volfile-servers=<server2>:<server3> where server2 and server3 also have bricks running. When server1 is down, and the volume is mounted again - server2 or server3 are queried to get the gluster volfiles.

@Jim, if this does not work, are you using 4.1.5 build with libgfapi access? If not, please provide the vdsm and gluster mount logs to analyse

If VMs go to paused state - this could mean the storage is not available. You can check "gluster volume status <volname>" to see if atleast 2 bricks are running.

On Fri, Sep 1, 2017 at 11:31 AM, Johan Bernhardsson <johan@kafit.se> wrote:
If gluster drops in quorum so that it has less votes than it should it will stop file operations until quorum is back to normal.If i rember it right you need two bricks to write for quorum to be met and that the arbiter only is a vote to avoid split brain.


Basically what you have is a raid5 solution without a spare. And when one disk dies it will run in degraded mode. And some raid systems will stop the raid until you have removed the disk or forced it to run anyway. 


/Johan

On Thu, 2017-08-31 at 22:33 -0700, Jim Kusznir wrote:
Hi all:  

Sorry to hijack the thread, but I was about to start essentially the same thread.

I have a 3 node cluster, all three are hosts and gluster nodes (replica 2 + arbitrar).  I DO have the mnt_options=backup-volfile-servers= set:

storage=192.168.8.11:/engine
mnt_options=backup-volfile-servers=192.168.8.12:192.168.8.13

I had an issue today where 192.168.8.11 went down.  ALL VMs immediately paused, including the engine (all VMs were running on host2:192.168.8.12).  I couldn't get any gluster stuff working until host1 (192.168.8.11) was restored.

What's wrong / what did I miss?

(this was set up "manually" through the article on setting up self-hosted gluster cluster back when 4.0 was new..I've upgraded it to 4.1 since).

Thanks!
--Jim


On Thu, Aug 31, 2017 at 12:31 PM, Charles Kozler <ckozleriii@gmail.com> wrote:
Typo..."Set it up and then failed that **HOST**"

And upon that host going down, the storage domain went down. I only have hosted storage domain and this new one - is this why the DC went down and no SPM could be elected?

I dont recall this working this way in early 4.0 or 3.6

On Thu, Aug 31, 2017 at 3:30 PM, Charles Kozler <ckozleriii@gmail.com> wrote:
So I've tested this today and I failed a node. Specifically, I setup a glusterfs domain and selected "host to use: node1". Set it up and then failed that VM

However, this did not work and the datacenter went down. My engine stayed up, however, it seems configuring a domain to pin to a host to use will obviously cause it to fail

This seems counter-intuitive to the point of glusterfs or any redundant storage. If a single host has to be tied to its function, this introduces a single point of failure

Am I missing something obvious?

On Thu, Aug 31, 2017 at 9:43 AM, Kasturi Narra <knarra@redhat.com> wrote:
yes, right.  What you can do is edit the hosted-engine.conf file and there is a parameter as shown below [1] and replace h2 and h3 with your second and third storage servers. Then you will need to restart ovirt-ha-agent and ovirt-ha-broker services in all the nodes .

[1] 'mnt_options=backup-volfile-servers=<h2>:<h3>' 

On Thu, Aug 31, 2017 at 5:54 PM, Charles Kozler <ckozleriii@gmail.com> wrote:
Hi Kasturi -

Thanks for feedback

> If cockpit+gdeploy plugin would be have been used then that would have automatically detected glusterfs replica 3 volume created during Hosted Engine deployment and this question would not have been asked
  
Actually, doing hosted-engine --deploy it too also auto detects glusterfs.  I know glusterfs fuse client has the ability to failover between all nodes in cluster, but I am still curious given the fact that I see in ovirt config node1:/engine (being node1 I set it to in hosted-engine --deploy). So my concern was to ensure and find out exactly how engine works when one node goes away and the fuse client moves over to the other node in the gluster cluster

But you did somewhat answer my question, the answer seems to be no (as default) and I will have to use hosted-engine.conf and change the parameter as you list

So I need to do something manual to create HA for engine on gluster? Yes?

Thanks so much!

On Thu, Aug 31, 2017 at 3:03 AM, Kasturi Narra <knarra@redhat.com> wrote:
Hi,

   During Hosted Engine setup question about glusterfs volume is being asked because you have setup the volumes yourself. If cockpit+gdeploy plugin would be have been used then that would have automatically detected glusterfs replica 3 volume created during Hosted Engine deployment and this question would not have been asked.

   During new storage domain creation when glusterfs is selected there is a feature called 'use managed gluster volumes' and upon checking this all glusterfs volumes managed will be listed and you could choose the volume of your choice from the dropdown list.

    There is a conf file called /etc/hosted-engine/hosted-engine.conf where there is a parameter called backup-volfile-servers="h1:h2" and if one of the gluster node goes down engine uses this parameter to provide ha / failover. 

 Hope this helps !!

Thanks
kasturi



On Wed, Aug 30, 2017 at 8:09 PM, Charles Kozler <ckozleriii@gmail.com> wrote:
Hello -

I have successfully created a hyperconverged hosted engine setup consisting of 3 nodes - 2 for VM's and the third purely for storage. I manually configured it all, did not use ovirt node or anything. Built the gluster volumes myself

However, I noticed that when setting up the hosted engine and even when adding a new storage domain with glusterfs type, it still asks for hostname:/volumename

This leads me to believe that if that one node goes down (ex: node1:/data), then ovirt engine wont be able to communicate with that volume because its trying to reach it on node 1 and thus, go down

I know glusterfs fuse client can connect to all nodes to provide failover/ha but how does the engine handle this?

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