SCI-CD

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h1. FAILOVER management

designations:

<pre>

gnt# - command exec on master node

gntX# - command exec on ordinary node

gntY# - command exec on other node

# - command exec on any node

</pre>

h2. Start instances on one node where other is down

When node starts and can't find other node, cluster management daemon ganeti-masterd don't start automatically, even on a master-node.

It is because of not able to find out if second node down or there is a link problem when instances on other node is still running.

Cluster management daemon start:

<pre>

gnt# ganeti-masterd --no-voting

</pre>

h2. Master node change in normal mode

Both of the nodes are online, master node changing is in normal mode

On master-candidate (gntX):

<pre>

gntX# gnt-cluster master-failover

</pre>

h2. Failure of master node

Master node(in this example gnt1) is down by hardware failure.

Start management daemon on master-candidate(gntX):

<pre>

gntX# ganeti-masterd --no-voting

</pre>

Activate new master node:

<pre>

gntX# gnt-cluster master-failover --no-voting

</pre>

+*Set broken node to offline so master node don't try to connect it.*+

-С = master-candidate

-O = offline

<pre>

gnt# gnt-node modify -C no -O yes gntY

</pre>

Start all instances from broken node on backup node:

<pre>

gnt# gnt-node failover --ignore-consistency gnt1

</pre>

h2. Set broken node to online

Old master node will not start management daemon on boot:

* if it will not find other node,

* if it will find other node that is in master mode.

If data on this node is ok then to readd it in claster:

Copy new configuration on it from new master node:

<pre>

gnt# gnt-cluster redist-conf

</pre>

Restart ganeti daemons:

<pre>

gntX# /etc/init.d/ganeti restart

</pre>

h2. Planned node turning off for maintenance

Migrate all instances from this node to another

<pre>

gnt# gnt-instance migrate INSTANCE

</pre>

If turning off node is master then you must to assign new cluster master(see above *Master node change in normal mode*)

Set node to offline and not master-candidate:

<pre>

gnt# gnt-node modify -C no -O yes УЗЕЛ

</pre>

Now you can simply turn off this node

h3. Returning node to online

After boot set node online and master-candidate:

<pre>

gnt# gnt-node modify -C yes -O no УЗЕЛ

</pre>

However, if you have any doubt about node's health, you would rather exec this:

<pre>

gnt# gnt-node add --readd УЗЕЛ

</pre> 

Anyway, you must wait about 5 minutes until watcher daemon set up drbd resources or initiate set up by hand:

<pre>

gnt# gnt-cluster verify-disks

</pre>

h2. Node replace to new

Add node to cluster:

<pre>

gnt# gnt-node add --readd gntX

</pre>

For all instances which new node is secondary:

<pre>

gnt# gnt-instance replace-disks --submit -s INSTANCE

</pre>

Readd node to puppet:

<pre>

gnt# gnt-instance console sci

sci# puppetca --clean gnt1.fqdn

</pre>

<pre>

gntX# /var/lib/puppet/ssl/*

gntX# /etc/init.d/puppet restart

</pre>

h2. Hard disk replace

Copy partitions from existent hdd(allowed only for same mode disks):

<pre>

# sfdisk -d /dev/sda|sfdisk /dev/sdX

</pre>

Check:

<pre>

# fdisk -l

</pre>

add to RAID:

<pre>

# mdadm --manage /dev/md0 --add /dev/sdX1

# mdadm --manage /dev/md1 --add /dev/sdX2

# mdadm --manage /dev/md2 --add /dev/sdX3

</pre>

Check:

<pre>

cat /proc/mdstat

</pre>