Create and export a GlusterFS volume with NFS-Ganesha in CentOS 8

GlusterFS built-in NFS server supports only NFS version 3. GlusterFS offers NFS exports using NFS-Ganesha, which supports NFS version 3 and 4 protocols.
NFS-Ganesha server is a user-mode file sharing server, which offers a GlusterFS plugin to export GlusterFS volumes. In the following article, the NSF-Ganesha and GlusterFS are installed and a simple GlusterFS volume is created and then exported through NFS 3 and 4 version protocols.
The version of the software in this article:

  • CentOS Stream release 8 (25.04.2021)
  • GlusterFS 8.4
  • NFS-Ganesha 3.5

STEP 1) Install GlusterFS.

dnf install -y centos-release-gluster
dnf install -y glusterfs-server

The first line will installs a new repository under the SIG management – https://wiki.centos.org/SpecialInterestGroup/Storage. The second line installs the GlusterFS server.

STEP 2) Install NFS-Ganesha.

dnf install -y centos-release-nfs-ganesha30
dnf install -y nfs-ganesha nfs-ganesha-gluster

The first line again installs a new repository under the SIG management and the second line installs the NFS-Ganesha server with Gluster plugin.

STEP 3) Create GlusterFS volume

Start the GlusterFS server and create a simple 3 replicas volume with:
Start the GlusterFS on all the three nodes and enable the GlusterFS communication between the three nodes using firewall-cmd utility. So execute the following commands:

systemctl start glusterd
firewall-cmd --permanent --new-zone=glusternodes
firewall-cmd --permanent --zone=glusternodes --add-source=192.168.0.200
firewall-cmd --permanent --zone=glusternodes --add-source=192.168.0.201
firewall-cmd --permanent --zone=glusternodes --add-source=192.168.0.202
firewall-cmd --permanent --zone=glusternodes --add-service=glusterfs
firewall-cmd --reload

On the first node create the GlusterFS volume. First, add the glnode2 and glnode3 to the cluster.

gluster peer probe glnode2
gluster peer probe glnode3
gluster volume create VOL1 replica 3 transport tcp glnode1:/mnt/storage/gluster/brick glnode2:/mnt/storage/gluster/brick glnode3:/mnt/storage/gluster/brick
gluster volume start VOL1

Keep on reading!

Stopping the glusterfs volume releases disk sleep process hangs

A quick tip for GlusterFS volume. There are multiple possible reasons for a Linux process to hang in “Disk Sleep” state, which even the KILL -9 cannot interrupt:

  • a bug in GlusterFS
  • just bad options turn on online
  • other device relying on a GlusterFS, which is unavailable.
[17294588.184470] INFO: task gdisk:12505 blocked for more than 120 seconds.
[17294588.184538] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[17294588.184628] gdisk           D ffff8ce01fb9acc0     0 12505  26866 0x00000080
[17294588.184780] Call Trace:
[17294588.184844]  [<ffffffffbaed3d81>] ? __wake_up_common_lock+0x91/0xc0
[17294588.184910]  [<ffffffffbb585da9>] schedule+0x29/0x70
[17294588.184974]  [<ffffffffbb5838b1>] schedule_timeout+0x221/0x2d0
[17294588.185037]  [<ffffffffbaed3dc3>] ? __wake_up+0x13/0x20
[17294588.185102]  [<ffffffffc0a05d2e>] ? loop_make_request+0x12e/0x210 [loop]
[17294588.185169]  [<ffffffffbaf06d32>] ? ktime_get_ts64+0x52/0xf0
[17294588.185232]  [<ffffffffbb58549d>] io_schedule_timeout+0xad/0x130
[17294588.185304]  [<ffffffffbb5863dd>] wait_for_completion_io+0xfd/0x140
[17294588.185369]  [<ffffffffbaedb990>] ? wake_up_state+0x20/0x20
[17294588.185468]  [<ffffffffbb157e64>] blkdev_issue_flush+0xb4/0x110
[17294588.185533]  [<ffffffffbb08d335>] blkdev_fsync+0x35/0x50
[17294588.185598]  [<ffffffffbb082f57>] do_fsync+0x67/0xb0
[17294588.185671]  [<ffffffffbb083240>] SyS_fsync+0x10/0x20
[17294588.185734]  [<ffffffffbb592ed2>] system_call_fastpath+0x25/0x2a
[17294708.187598] INFO: task gdisk:12505 blocked for more than 120 seconds.
[17294708.187664] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[17294708.187753] gdisk           D ffff8ce01fb9acc0     0 12505  26866 0x00000080
[17294708.187905] Call Trace:
[17294708.187968]  [<ffffffffbaed3d81>] ? __wake_up_common_lock+0x91/0xc0
[17294708.188033]  [<ffffffffbb585da9>] schedule+0x29/0x70
[17294708.188096]  [<ffffffffbb5838b1>] schedule_timeout+0x221/0x2d0
[17294708.188159]  [<ffffffffbaed3dc3>] ? __wake_up+0x13/0x20
[17294708.188223]  [<ffffffffc0a05d2e>] ? loop_make_request+0x12e/0x210 [loop]
[17294708.188289]  [<ffffffffbaf06d32>] ? ktime_get_ts64+0x52/0xf0
[17294708.188352]  [<ffffffffbb58549d>] io_schedule_timeout+0xad/0x130
[17294708.188416]  [<ffffffffbb5863dd>] wait_for_completion_io+0xfd/0x140
[17294708.188480]  [<ffffffffbaedb990>] ? wake_up_state+0x20/0x20
[17294708.188545]  [<ffffffffbb157e64>] blkdev_issue_flush+0xb4/0x110
[17294708.188624]  [<ffffffffbb08d335>] blkdev_fsync+0x35/0x50
[17294708.188690]  [<ffffffffbb082f57>] do_fsync+0x67/0xb0
[17294708.188754]  [<ffffffffbb083240>] SyS_fsync+0x10/0x20
[17294708.188828]  [<ffffffffbb592ed2>] system_call_fastpath+0x25/0x2a

The above example of dmesg log shows the gdisk process stuck in “Disk Sleep” state, because of a loop device from a file on an unavailable GlusterFS volume! Kill -9 won’t help, the process will remain in this bad state and even a restart would be difficult to perform!

[root@srv1 ~]# gluster volume stop VOL2 
Stopping volume will make its data inaccessible. Do you want to continue? (y/n) y
volume stop: VOL2: success
[root@srv1 ~]# gluster volume start VOL2 
volume start: VOL2: success

The solution is to stop the GlusterFS Volume and all the blocked processes on bad devices such as above would be released. The processes will carry on executing or will end their execution after issuing a stop command to the volume. No problem to start the GlusterFS volume immediately after the stop!
NOTE: executing STOP command would affect all servers using this volume. The volume becomes inaccessible for all!