NFS4 High Availability setup - Traditional integration

This howto describes a NFS4 Only HA service setup using the least possible virtualization layers (no persistent volume, no cluster backend network ip address, no ingress gateway, no container), to maximize efficiency and simplicity.

It has been tested on Red Hat Enterprise Linux 8.7 nodes.

Content:

Prerequisites

Prerequisite

Example

2 nodes
node1 5.196.34.132
node2 5.196.34.133

A failover ip address for NFS4 server

nfsv4.opensvc.com 5.196.34.141

Shared storage (san, iscsi, …) or drbd

OpenSVC agent 2.1+ installed

Setup LVM2

Configure a lvm2 volume group, to host a lvm2 logical volume to use as the drbd backing device

dnf -y install lvm2
pvcreate /dev/vdb
vgcreate datavg /dev/vdb

Setup DRBD

Kernel module & utils

Linbit DRBD kernel modules for RHEL are available on ElRepo

dnf -y install https://www.elrepo.org/elrepo-release-8.el8.elrepo.noarch.rpm
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sed -i 's/^mirrorlist/#mirrorlist/' /etc/yum.repos.d/elrepo.repo
dnf -y install kmod-drbd90 drbd90-utils

You can verify that drbd is ready with the command below

[root@node1 ~]# modinfo drbd | grep ^version
version:        9.1.13

Setup the OpenSVC Cluster

Install OpenSVC

On both nodes

dnf -y install python3 python3-cryptography
curl -o opensvc-2.1-latest.rpm https://repo.opensvc.com/rpms/2.1/current
dnf -y install ./opensvc-2.1-latest.rpm

Join cluster nodes

On node1

[root@node1 ~]# om cluster set --kw hb#1.type=unicast
[root@node1 ~]# om cluster set --kw cluster.name=cluster1
[root@node1 ~]# om cluster get --kw cluster.secret
b26a1e28b84a11edab28525400d67af6

On node2

[root@node2 ~]# om daemon join --node node1 --secret b26a1e28b84a11edab28525400d67af6
@ n:node2
local node is already frozen
join node node1
W local node is left frozen as it was already before join

On node1

Unfreeze nodes and setup root ssh trust:

om node thaw
om node update ssh authorized keys --node='*'

Note

Ensure that you can ssh as root from one node to another without being prompted for a password

You should now have a configured cluster, like:

[root@node1 ~]# om mon
Threads                               node1        node2
 daemon         running             |
 hb#1.rx        running  [::]:10000 | /            O
 hb#1.tx        running             | /            O
 listener       running       :1214
 monitor        running
 scheduler      running

Nodes                                 node1        node2
 score                              | 69           69
  load 15m                          | 0.0          0.0
  mem                               | 12/98%:1.77g 11/98%:1.77g
  swap                              | -            -
 state                              |

*/svc/*                               node1        node2

Deploy the service

Deploy with NFS4 disabled

Create the opensvc service using the name nfsv4, in the test namespace, storing a 5G drbd filesystem in datavg lvm2 volume group, reachable using the public dns name nfsv4.opensvc.com configured on interface named eth0

On node1

om test/svc/nfsv4 deploy \
--config https://raw.githubusercontent.com/opensvc/opensvc_templates/main/nfs/nfsv4-app-disabled.conf \
--env vg=datavg \
--env size=5G \
--env fqdn=nfsv4.opensvc.com \
--env nic=eth0

Note

The config used in this command has all application ressources (nfsdcld, rpc.idmapd, rpc.mountd, nfsd) disabled. Using that trick, we can configure NFS4 later, and test core (ip, disk, fs) failovers early.

This is convenient for tutoring, but in other situations you may want to use –config https://raw.githubusercontent.com/opensvc/opensvc_templates/main/nfs/nfsv4.conf for a one-step deployment.

This command creates and configures the system resources needed by the service on both nodes:

  • 5GB logical volume in datavg volume group

  • drbd ressources on both nodes (creation and synchronisation)

  • ext4 filesystem

After a few minutes (DRBD synchronisation time), you should end up in this situation:


    [root@node1 ~]# om test/svc/nfsv4 print status -r
    test/svc/nfsv4                   up        
    `- instances
       |- node2                      stdby up   idle
       `- node1                      up         idle, started
          |- ip#1           ........ up         5.196.34.141/255.255.255.224 eth0 nfsv4.opensvc.com
          |- disk#1         ......S. stdby up   lv datavg/nfsv4.test.svc.cluster1
          |- disk#2         ......S. stdby up   drbd nfsv4.test.svc.cluster1
          |                                     info: Primary
          |- fs#1           ........ up         ext4 /dev/drbd0@/srv/nfsv4.test.svc.cluster1
          |- app#1          ..D../.. n/a        simple: nfsdcld
          |- app#2          ..D../.. n/a        simple: rpc.idmapd
          |- app#3          ..D../.. n/a        forking: rpc.nfsd
          |- app#4          ..D../.. n/a        simple: rpc.mountd
          `- sync#i0        ..DO./.. n/a        rsync svc config to nodes

    [root@node1 ~]# df -h /srv/nfsv4.test.svc.cluster1
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/drbd1      4,9G   40K  4,6G   1% /srv/nfsv4.test.svc.cluster1

    [root@node1 ~]# drbdadm status
    nfsv4.test.svc.cluster1 role:Primary
      disk:UpToDate
      node2 role:Secondary
        peer-disk:UpToDate

Test the core failover

This step is only useful to ensure ip, drbd and filesystem fails over forth and back between nodes, before continuing with the the NFS4 layer setup.

Initial situation

The green O means that the service is currently running on node1

On node1 or node2

[root@node1 ~]# om test/svc/nfsv4 mon
test/svc/nfsv4                   node1 node2
 test/svc/nfsv4 up ha    1/1   | O^    S

Move service to node2

The switch action will relocate the service to the other node. The red ^ means that the service is not running on its preferred node.

On node1 or node2

    [root@node1 ~]# om test/svc/nfsv4 switch
    @ n:node1 o:test/svc/nfsv4 sc:n
    test/svc/nfsv4 defer target state set to placed@node2

    [root@node1 ~]# om test/svc/nfsv4 mon
    test/svc/nfsv4                    node1 node2
     test/svc/nfsv4 up^ ha    1/1   | S^    O

Move back service to node1

We can use either switch action, or giveback to move the service to its preferred node.

On node1 or node2

    [root@node1 ~]# om test/svc/nfsv4 giveback
    @ n:node1 o:test/svc/nfsv4 sc:n
    test/svc/nfsv4 defer target state set to placed

    [root@node1 ~]# om test/svc/nfsv4 mon
    test/svc/nfsv4                   node1 node2
     test/svc/nfsv4 up ha    1/1   | O^    S

Enable NFS4

We have to make sure systemd won’t manage NFS4 services, only OpenSVC must be in charge of this servers.

Download NFS4 server config files

The NFS4 configuration files are stored into the replicated filesystem.

On node1

curl -o /srv/nfsv4.test.svc.cluster1/etc/nfs.conf \
  https://raw.githubusercontent.com/opensvc/opensvc_templates/main/nfs/etc.nfs.conf

curl -o /srv/nfsv4.test.svc.cluster1/etc/exports \
  https://raw.githubusercontent.com/opensvc/opensvc_templates/main/nfs/etc.exports.conf

Install NFS4 server config files

On noth nodes

rm -f /etc/nfs.conf ; rm -f /etc/exports ; rmdir /etc/exports.d
ln -s /srv/nfsv4.test.svc.cluster1/etc/nfs.conf /etc/nfs.conf
ln -s /srv/nfsv4.test.svc.cluster1/etc/exports /etc/exports

Adjust the config files

On node1

sed -i 's@ROOTFS@/srv/nfsv4.test.svc.cluster1@' /srv/nfsv4.test.svc.cluster1/etc/nfs.conf
sed -i 's@FQDN@nfsv4.opensvc.com@' /srv/nfsv4.test.svc.cluster1/etc/nfs.conf
sed -i 's@ROOTFS@/srv/nfsv4.test.svc.cluster1@' /srv/nfsv4.test.svc.cluster1/etc/exports

Enable & start OpenSVC app resources

On node1

    [root@node1 ~]# om test/svc/nfsv4 enable --rid app
    @ n:node1 o:test/svc/nfsv4 sc:n
    remove app#3.disable
    remove app#2.disable
    remove app#1.disable
    remove app#4.disable

    [root@node1 ~]# om test/svc/nfsv4 start --rid app
    @ n:node1 o:test/svc/nfsv4 r:app#1 sc:n
    exec '/usr/sbin/nfsdcld --foreground' as user root
    @ n:node1 o:test/svc/nfsv4 r:app#2 sc:n
    exec '/usr/sbin/rpc.idmapd -f' as user root
    @ n:node1 o:test/svc/nfsv4 r:app#3 sc:n
    pre_start: /usr/sbin/exportfs -r
    exec /usr/sbin/rpc.nfsd 8 as user root
    start done in 0:00:00.403523 - ret 0
    post_start: /bin/sh -c 'if systemctl -q is-active gssproxy; then systemctl reload gssproxy ; fi'
    @ n:node1 o:test/svc/nfsv4 r:app#4 sc:n
    exec '/usr/sbin/rpc.mountd --foreground' as user root

    [root@node1 ~]# om test/svc/nfsv4 print status -r
    test/svc/nfsv4                   up        
    `- instances
       |- node2                      stdby up   idle
       `- node1                      up         idle, started
          |- ip#1           ........ up         5.196.34.141/255.255.255.224 eth0 nfsv4.opensvc.com
          |- disk#1         ......S. stdby up   lv datavg/nfsv4.test.svc.cluster1
          |- disk#2         ......S. stdby up   drbd nfsv4.test.svc.cluster1
          |                                     info: Primary
          |- fs#1           ........ up         ext4 /dev/drbd0@/srv/nfsv4.test.svc.cluster1
          |- app#1          ...../.. up         simple: nfsdcld
          |- app#2          ...../.. up         simple: rpc.idmapd
          |- app#3          ...../.. up         forking: rpc.nfsd
          |- app#4          ...../.. up         simple: rpc.mountd
          `- sync#i0        ..DO./.. n/a        rsync svc config to nodes

Test

Connect clients

You should be able to mount the nfsroot share from any client.

[root@client ~]# mount -v -t nfs4 -o proto=tcp,port=2049 nfsv4.opensvc.com:/ /mnt
mount.nfs4: timeout set for Thu Mar  2 17:11:37 2023
mount.nfs4: trying text-based options 'proto=tcp,port=2049,vers=4.2,addr=5.196.34.141,clientaddr=37.59.71.10'

[root@client ~]# df -h /mnt
Filesystem           Size   Used  Avail Use% Mounted on
nfsv4.opensvc.com:/  4860M     0  4560M   0% /mnt

Test the failover

Start nfs clients activity (fio runs for example).

Reboot the node hosting the active service instance.

Warning

Please note that this howto uses the default NFS4 security and tuning configurations. You may now tune the NFS4 configuration to your specific context requirements.