GlusterFS VFS plugin for Samba

Here are the topics this blog is going to cover.

  • Samba Server
  • Samba VFS
  • Libgfapi
  • GlusterFS VFS plugin for Samba and libgfapi
  • Without GlusterFS VFS plugin
  • FUSE mount vs VFS plugin

About Samba Server:

Samba server runs on Unix and Linux/GNU operating systems. Windows clients can talk to Linux/GNU/Unix systems through Samba server. It provides the interoperability between Windows and Linux/Unix systems. Initially it was created to provide printer sharing and file sharing mechanisms between Unix/Linux and Windows. As of now Samba project is doing much more than just file and printer sharing.

Samba server works as a semantic translation engine/machine. Windows clients talk in Windows syntax e.g. SMB protocol. And Unix/Linux/GNU file-systems understand requests in  POSIX. Samba converts Windows syntax to *nix/GNU syntax and vice versa.

This article is about Samba integration with GlusterFS.  For specific details I have taken example of GlusterFS deployed on Linux/GNU.

If you have never heard of Samba project before, you should read about it more , before going further in to this blog.

Here are important link/pointers for further study:

  1. what is Samba?
  2. Samba introduction

Samba VFS:

Samba code is very modular in nature. Samba VFS code is divided in to two parts i.e. Samba VFS layer and VFS modules.

The purpose of Samba VFS layer is to act as an interface between Samba server and  below layers. When Samba server get requests from Windows clients through SMB protocol requests, it passes it to Samba VFS modules.

Samba VFS modules i.e. plugin is a shared library (.so) and it implements some or all functions which Samba VFS layer i.e. interface makes  available.  Samba VFS modules can be stacked on each other(if they are designed to be stacked).

For more about Samba VFS layer, please refer http://unix4.com/w/writing-a-samba-vfs-richard-sharpe-2-oct-2011-e6438-pdf.pdf

Samba VFS layer passes the request to VFS modules. If the Samba share is done for a native Linux/Unix file-system, the call goes to default VFS module. The default VFS module forwards call to System layer i.e. operating system. For User space file-system like GlusterFS, VFS layer calls are implemented through a VFS module i.e. VFS plugin for GlusterFS .The plugin redirects the requests (i.e fops) to GlusterFS APIs i.e. libgfapi. It implements or maps all VFS layer calls using libgfapi.

libgfapi:

libgfapi (i.e. glusterfs api) is set of APIs which can directly talk to GlusterFS. Libgfapi is another access method for GlusterFS like NFS, SMB and FUSE. Libgfapi bindings are available for C, Python, Go and more programming languages. Applications can be developed which can directly use GlusterFS without a GlusterFS volume mount.

 GlusterFS VFS plugin for Samba and libgfapi:

Here is the schematic diagram of how communication works between different layers.

gluster-samba-vfs-plugin

Samba Server:  This represents Samba Server and Samba VFS layer

VFS plugin for GlusterFS: This implements or maps relevant VFS layer fops to libgfapi calls.

glusterd: Management daemon of Glusterfs node i.e. server.

glusterfsd: Brick process of Glusterfs node i.e. server.

The client requests come to Samba server and Samba servers redirects the calls to GlusterFS’s VFS plugin through Samba VFS layer. VFS plugin calls relevant libgfapi fucntions. Libgfapi acts as a client, contacts glusterd for vol file information ( i.e. information about gluster volume, translators, involved nodes) , then forward requests to appropriate glusterfsd i.e. brick processes where requests actually get serviced.

If you want to know specifics about the setup to share GlusterFS’s volume through Samba VFS plugin, refer below link.

https://lalatendumohanty.wordpress.com/2014/02/11/using-glusterfs-with-samba-and-samba-vfs-plugin-for-glusterfs-on-fedora-20/

Without GlusterFS VFS plugin: 

Without GlusterFS VFS plugin, we can still share GlusterFS volume through Samba server. This can be done through native glusterfs mount i.e. FUSE (file system in user space). We need to mount the volume using FUSE i.e .glusterfs native mount in the same machine where Samba server is running, then share the mount point using Samba server. As we are not using the VFS plugin for GlusterFS here, Samba will treat the mounted GlusterFS volume as a native file-system. The default VFS module will be used and the file-system calls will be sent to operating system. The flow is same as any native file system shared through Samba.

FUSE mount vs VFS plugin:

If you are not familiar with file systems in user space,  please read about FUSE i.e. file system in user space.

For FUSE mounts, file system fops from Samba server goes to user space FUSE mount point -> Kernel VFS -> /dev/fuse -> GlusterFS and comes back in the same path. Refer to below diagrams for details. Consider Samba server as an application which runs on the fuse mount point.

Fuse_Mount

Fuse mount architecture for GlusterFS

You can observe the process context switches happens between user and kernel space in above architecture. It is going to be a key differentiation factor when compared with libgfapi based VFS plugin.

For Samba VFS plugin implementation, see the below diagram. With the plugin Samba calls get converted to libgfapi calls and libgfapi forward the requests  to GlusterFS.

libgfapi

Libgfapi architecture for GlusterFS

The above pictures are copied from this presentation:

Advantage of libgfapi based Samba plugin Vs FUSE mount:

  • With libgfapi , there are no kernel VFS layer context switches. This results in performance benefits compared to  FUSE mount.
  • With a separate Samba VFS module i.e. plugin , features ( e.g: more NTFS functionality) can be provided in GlusterFS and it can be supported with Samba, which native Linux file systems do not support.

 

 

 

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Using GlusterFS With GlusterFS Samba vfs plugin on Fedora

This blog covers the steps and implementation details to use GlusterFS Samba VFS plugin.

Please refer below link, If you are looking for architectural information for GlusterFS Samba VFS plugin,  difference between FUSE mount vs Samba VFS plugin

https://lalatendumohanty.wordpress.com/2014/04/20/glusterfs-vfs-plugin-for-samba/

I have setup  two node GlusterFS cluster with Fedora 20 (minimal install) VMs. Each VM has 3 separate XFS partitions with each partitions 100GB each.
One of the Gluster node is used as a Samba server in this setup.

I had originally tested this with Fedora 20. But this example should work fine with latest Fedoras i.e. F21 and F22

GlusterFS Version: glusterfs-3.4.2-1.fc20.x86_64

Samba version:  samba-4.1.3-2.fc20.x86_64

Post installation “df -h” command looked like below in the VMs
$df -h
Filesystem                            Size  Used Avail Use% Mounted on
/dev/mapper/fedora_dhcp159–242-root   50G  2.2G   45G   5% /
devtmpfs                              2.0G     0  2.0G   0% /dev
tmpfs                                 2.0G     0  2.0G   0% /dev/shm
tmpfs                                 2.0G  432K  2.0G   1% /run
tmpfs                                 2.0G     0  2.0G   0% /sys/fs/cgroup
tmpfs                                 2.0G     0  2.0G   0% /tmp
/dev/vda1                             477M  103M  345M  23% /boot
/dev/mapper/fedora_dhcp159–242-home   45G   52M   43G   1% /home
/dev/mapper/gluster_vg1-gluster_lv1           100G  539M  100G   1% /gluster/brick1
/dev/mapper/gluster_vg2-gluster_lv2           100G  406M  100G   1% /gluster/brick2
/dev/mapper/gluster_vg3-gluster_lv3           100G   33M  100G   1% /gluster/brick3

You can use following commands to create xfs partitions
1. pvcreate /dev/vdb
2. vgcreate VG_NAME /dev/vdb
3. lvcreate -n LV_NAME -l 100%PVS VG_NAME /dev/vdb
4. mkfs.xfs -i size=512 LV_PATH

Following are the steps and packages need to be performed/installed on each node (which is Fedora 20 for mine)

#Change SELinux to either “permissive” or “disabled” mode

# To put SELinux in permissive mode
$setenforce 0

#To see the current mode of SELinux

$getenforce

SELinux policy rules for Gluster is present in recent Fedora releases e.g. F21, F22 or later. So SELinux should work fine with Gluster.

#Remove all iptable rules, so that it does not interfare with Gluster

$iptables -F

yum install glusterfs-server
yum install samba-vfs-glusterfs
yum install samba-client

#samba-vfs-glusterfs RPMs for CentOS, RHEL, Fedora19/18 are avialable at http://download.gluster.org/pub/gluster/glusterfs/samba/

#To start glusterd and auto start it after boot
$systemctl start glusterd
$systemctl enable glusterd
$systemctl status glusterd

#To start smb and auto start it after boot
$systemctl start smb
$systemctl enable smb
$systemctl status smb

#Create gluster volume and start it. (Running below commands from Server1_IP)

$gluster peer probe Server2_IP
$gluster peer status
Number of Peers: 1

Hostname: Server2_IP
Port: 24007
Uuid: aa6f71d9-0dfe-4261-a2cd-5f281632aaeb
State: Peer in Cluster (Connected)
$gluster v create testvol Server2_IP:/gluster/brick1/testvol-b1 Server1_IP:/gluster/brick1/testvol-b2
$gluster v start testvol

#Modify smb.conf for Samba share

$vi /etc/samba/smb.conf

#
[testvol]
comment = For samba share of volume testvol
path = /
read only = No
guest ok = Yes
kernel share modes = No
vfs objects = glusterfs
glusterfs:loglevel = 7
glusterfs:logfile = /var/log/samba/glusterfs-testvol.log
glusterfs:volume = testvol

#For debug logs you can change the log levels to 10 e.g: “glusterfs:loglevel = 10”

# Do not miss “kernel share modes = No” else you won’t be able to write anything in to the share

#verify that your changes are correctly understood by Samba
$testparm -s
Load smb config files from /etc/samba/smb.conf
rlimit_max: increasing rlimit_max (1024) to minimum Windows limit (16384)
Processing section “[homes]”
Processing section “[printers]”
Processing section “[testvol]”
Loaded services file OK.
Server role: ROLE_STANDALONE
[global]
workgroup = MYGROUP
server string = Samba Server Version %v
log file = /var/log/samba/log.%m
max log size = 50
idmap config * : backend = tdb
cups options = raw

[homes]
comment = Home Directories
read only = No
browseable = No

[printers]
comment = All Printers
path = /var/spool/samba
printable = Yes
print ok = Yes
browseable = No

[testvol]
comment = For samba share of volume testvol
path = /
read only = No
guest ok = Yes
kernel share modes = No
vfs objects = glusterfs
glusterfs:loglevel = 10
glusterfs:logfile = /var/log/samba/glusterfs-testvol.log
glusterfs:volume = testvol

#Restart the Samba service. This not a compulsory step as Samba takes latest smb.conf for new connections. But to make sure it uses the latest smb.conf, restart the service.
$systemctl  restart smb

#Set smbpasswd for root. This will be used for mounting the volume/Samba share on the client
$smbpasswd -a root

#Mount the cifs share using following command and it is ready for use 🙂
mount -t cifs -o username=root,password=<smbpassword> //Server1_IP/testvol /mnt/cifs

GlusterFS volume tuning for volume shared through Samba:

  • Gluster volume needs to have: “gluster volume set volname server.allow-insecure on”
  • /etc/glusterfs/glusterd.vol of each of gluster node
    add “option rpc-auth-allow-insecure on”
  • Restart glusterd of each node.

For setups where Samba server and Gluster nodes need to be on different machines:

# put “glusterfs:volfile_server = <server name/ip>” in the smb.conf settings for the specific  volume

e.g:

[testvol]
comment = For samba share of volume testvol
path = /
read only = No
guest ok = Yes
kernel share modes = No
vfs objects = glusterfs
glusterfs:loglevel = 7
glusterfs:logfile = /var/log/samba/glusterfs-testvol.log

glusterfs:volfile_server = <server name/ip>
glusterfs:volume = testvol

#Here are the packages that were installed on the nodes

rpm -qa | grep gluster
glusterfs-libs-3.4.2-1.fc20.x86_64
glusterfs-api-3.4.2-1.fc20.x86_64
glusterfs-3.4.2-1.fc20.x86_64
glusterfs-cli-3.4.2-1.fc20.x86_64
glusterfs-server-3.4.2-1.fc20.x86_64
samba-vfs-glusterfs-4.1.3-2.fc20.x86_64
glusterfs-devel-3.4.2-1.fc20.x86_64
glusterfs-fuse-3.4.2-1.fc20.x86_64
glusterfs-api-devel-3.4.2-1.fc20.x86_64

[root@dhcp159-242 ~]# rpm -qa | grep samba
samba-client-4.1.3-2.fc20.x86_64
samba-4.1.3-2.fc20.x86_64
samba-vfs-glusterfs-4.1.3-2.fc20.x86_64
samba-libs-4.1.3-2.fc20.x86_64
samba-common-4.1.3-2.fc20.x86_64

Note: The same smb.conf entries should work with CentOS6 too.