Accessing Gluster volume via SMB Protocol

Layered product Samba is used to export the Gluster volume and ctdb for providing the high availability Samba. Here are the steps to configure Highly Available Samba cluster to export Gluster volume.

Note: These configuration steps are applicable to Samba version = 4.1. and Gluster Version >= 3.7. ctdb >= 2.5

Step 1: Choose the servers that will export the Gluster volume.

The servers may/may not be part of the trusted storage pool. Preferable number of servers is <=4. Install Samba and ctdb packages on these servers.

Step 2: Enable/Disable the auto export of Gluster volume via SMB

# gluster volume set VOLNAME user.smb disable/enable

Step 3: Setup the CTDB Cluster:

Create a ctdb meta volume with replica N, N being the number of the servers that are used as Samba servers. This volume will host only a zero byte lock file, hence choose the minimal sized bricks. To create the n replica volume run the following command:
```
 # gluster volume create <volname> replica n <ipaddr/host name>:/<brick_patch>.... N times
```

In the following files, replace "all" in the statement "META=all" to the newly created volume name.

 /var/lib/glusterd/hooks/1/start/post/S29CTDBsetup.sh
 /var/lib/glusterd/hooks/1/stop/pre/S29CTDB-teardown.sh

Start the ctdb volume
```
# gluster vol start <volname>
```
Verify the following:
- If the following lines are added in smb.conf file in all the nodes running samba/ctdb:
```
clustering = yes
idmap backend = tdb2
```
- If the ctdb volume is mounted at /gluster/lock on all the nodes that runs ctdb/samba
- If the mount entry for ctdb volume is added in /etc/fstab
- If file /etc/sysconfig/ctdb exists on all the nodes that runs ctdb/samba
Create /etc/ctdb/nodes files on all the nodes that runs ctdb/samba, and add the IPs of all these nodes in the file. For example,
```
 # cat /etc/ctdb/nodes
 10.16.157.0
 10.16.157.3
 10.16.157.6
 10.16.157.8
```
The IPs listed here are the private IPs of Samba/ctdb servers, which should be a private non-routable subnet and are only used for internal cluster traffic. For more details refer to the ctdb man page.
Create /etc/ctdb/public_addresses files on all the nodes that runs ctdb/samba, and add the virtual IPs in the following format:
```
 <virtual IP><routing prefix> <node interface>
```
Eg:
```
 # cat /etc/ctdb/public_addresses
 192.168.1.20/24 eth0
 192.168.1.21/24 eth0
```
Either uncomment CTDB_SAMBA_SKIP_SHARE_CHECK=yes or add CTDB_SAMBA_SKIP_SHARE_CHECK=yes in its absence inside /etc/ctdb/script.options to disable checking of the shares by ctdb.
If SELinux is enabled and enforcing, try the following command if ctdb fails.
```
 # setsebool -P use_fusefs_home_dirs 1
 # setsebool -P samba_load_libgfapi 1
```

Step 4: Performance tunings before exporting the volume

To ensure lock and IO coherency:

# gluster volume set VOLNAME storage.batch-fsync-delay-usec 0

If using Samba 4.X version add the following line in smb.conf in the global section
```
 kernel share modes = no
 kernel oplocks = no
 map archive = no
 map hidden = no
 map read only = no
 map system = no
 store dos attributes = yes
```
Note: Setting 'store dos attributes = no' is recommended if archive/hidden/read-only dos attributes are not used. This can give better performance.

If you are using gluster5 or higher execute the following to improve performance:

 # gluster volume set VOLNAME group samba

On older version, please execute the following:

 # gluster volume set VOLNAME features.cache-invalidation on
 # gluster volume set VOLNAME features.cache-invalidation-timeout 600
 # gluster volume set VOLNAME performance.cache-samba-metadata on
 # gluster volume set VOLNAME performance.stat-prefetch on
 # gluster volume set VOLNAME performance.cache-invalidation on
 # gluster volume set VOLNAME performance.md-cache-timeout 600
 # gluster volume set VOLNAME network.inode-lru-limit 200000
 # gluster volume set VOLNAME performance.nl-cache on
 # gluster volume set VOLNAME performance.nl-cache-timeout 600
 # gluster volume set VOLNAME performance.readdir-ahead on
 # gluster volume set VOLNAME performance.parallel-readdir on

Tune the number of threads in gluster for better performance:

# gluster volume set VOLNAME client.event-threads 4
# gluster volume set VOLNAME server.event-threads 4 # Increasing to a very high value will reduce the performance

Step 5: Mount the volume using SMB

If no Active directory setup add the user on all the samba server and set the password
```
 # adduser USERNAME
 # smbpasswd -a USERNAME
```

Start the ctdb, smb and other related services:

# systemctl re/start ctdb
# ctdb status
# ctdb ip
# ctdb ping -n all

To verify if the volume exported by samba can be accessed by a user:
```
 # smbclient //<hostname>/gluster-<volname> -U <username>%<password>
```

To mount on a linux system:

 # mount -t cifs -o user=<username>,pass=<password> //<Virtual IP>/gluster-<volname> /<mountpoint>

To mount on Windows system:

 >net use <device:> \\<Virtual IP>\gluster-<volname>

OR

 \\<Virtual IP>\gluster-<volname>

from windows explorer.