all posts tagged raid

by on September 30, 2014

Gluster, CIFS, ZFS – kind of part 2

A while ago I put together a post detailing the installation and configuration of 2 hosts running glusterfs, which was then presented as CIFS based storage.

This post gained a bit of interest through the comments and social networks, one of the comments I got was from John Mark Walker suggesting I look at the samba-gluster vfs method instead of mounting the filesystem using fuse (directly access the volume from samba, instead of mounting then presenting). On top of this I’ve also been looking quite a bit at ZFS, whereas previously I had a Linux RAID as the base filesystem. So here is a slightly different approach to my previous post.

Getting prepared

As before, we’re looking at 2 hosts, virtual in the case of this build but more than likely physical in a real world scenario, either way it’s irrelevant. Both of these hosts are running CentOS 6 minimal installs (I’ll update to 7 at a later date), static IP addresses assigned and DNS entries created. I’ll also be running everything under a root session, if you don’t do the same just prefix the commands with sudo. For purposes of this I have also disabled SELINUX and removed all firewall rules. I will one day leave SELINUX enabled in this configuration but for now lets leave it out of the equation.

In my case these names and addresses are as follows:

arcstor01 –

arcstor02 –

First off lets get the relevant repositories installed (EPEL, ZFS and Gluster)

yum localinstall --nogpgcheck
yum localinstall --nogpgcheck
curl -o /etc/yum.repos.d/gluster.repo
curl -o /etc/yum.repos.d/glusterfs-samba-epel.repo

Local filesystem

As previously mentioned, this configuration will be hosted from 2 virtual machines, each will have 3 disks. 1 for the OS, and the other 2 to be used in a ZFS pool.

First off we need to install ZFS itself, once you have the above zfs-release repo installed this can be done with the following command:

yum install kernel-devel zfs

Perform this on both hosts.

We can now create a zfs pool. In my case the disk device names are vdX but they could be sdX,

fdisk -l

can help you identify the device names, whatever they are just replace them in the following commands.

Create a ZFS pool

zpool create -f  -m /gluster gluster mirror /dev/vdb /dev/vdc

this command will create a zfs pool mounted at /gluster, without -m /gluster it would mount at /{poolname} while in this case it’s the same I just added the option for clarity. The volume name is gluster, the redundancy level is mirrored which is similar to RAID1, there are a number of raid levels available in ZFS all are best explained here: The final element to the command is where to host the pool, in our case on /dev/vdb and /dev/vdc. The -f option specified is to force creation of the pool, this is required remove the need to create partitions prior to the creation of the pool.

Running the command

zpool status

Will return the status of the created pool, which if successful should look something similar to:

[root@arcstor01 ~]# zpool status
 pool: gluster
 state: ONLINE
 scan: none requested
 gluster ONLINE 0 0 0
 mirror-0 ONLINE 0 0 0
 vdb1 ONLINE 0 0 0
 vdc1 ONLINE 0 0 0

errors: No known data errors

A quick ls and df will also show us that the /gluster mountpoint is present and the pool is mounted, the df should show the size as being half the sum of both drives in the pool:

[root@arcstor01 ~]# ls /
 bin boot cgroup dev etc gluster home lib lib64 lost+found media mnt opt proc root sbin selinux srv sys tmp usr var
 [root@arcstor01 ~]# df -h
 Filesystem Size Used Avail Use% Mounted on
 /dev/vda1 15G 1.2G 13G 9% /
 tmpfs 498M 0 498M 0% /dev/shm
 gluster 20G 0 20G 0% /gluster

If this is the case, rinse and repeat on host 2. If this is also successful then we now have a resilient base filesystem on which to host our gluster volumes. There is a bucket load more to ZFS and it’s capabilities but it’s way outside the confines of this configuration, well worth looking into though.

Glusterising our pool

So now we have a filesystem, lets make it better. Next up, installing glusterfs, enabling it then preparing the directories, for this part it is pretty much identical to the previous post:

yum install glusterfs-server -y

chkconfig glusterd on

service glusterd start

mkdir  -p /gluster/bricks/share/brick1

This needs to be done on both hosts.

Now only on host1 lets make the two nodes friends, create and then start the gluster volume:

# gluster peer probe arcstor02
peer probe: success.

# gluster vol create share replica 2 arcstor01:/gluster/bricks/share/brick1 arcstor02:/gluster/bricks/share/brick1
volume create: share: success: please start the volume to access data

# gluster vol start share
volume start: share: success

[root@arcstor01 ~]# gluster vol info share

Volume Name: data1
Type: Replicate
Volume ID: 73df25d6-1689-430d-9da8-bff8b43d0e8b
Status: Started
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Brick1: arcstor01:/gluster/bricks/share1/brick1
Brick2: arcstor02:/gluster/bricks/share1/brick1

If all goes well above we should have a gluster volume ready to go, this volume will be presented via samba directly. For this configuration a locally available shared area is required, for this we will create another gluster volume to mount locally in which to store lockfiles and shared config files.

mkdir  -p /gluster/bricks/config/brick1
gluster vol create config replica 2 arcstor01:/gluster/bricks/config/brick1 arcstor02:/gluster/bricks/config/brick1
gluster vol start config
mkdir  /opt/samba-config
mount -t glusterfs localhost:config /opt/samba-config

The share volume could probably be used by using a different path in the samba config but for simplicity we’ll keep them seperate for now.
The mountpoint for /opt/samba-config will need to be added to fstab to ensure it mounts at boot time.

echo "localhost:config /opt/samba-config glusterfs defaults,_netdev 0 0" >>/etc/fstab

Should take care of that, remember that needs to be on both hosts.

Samba and CTDB

We now have a highly resilient datastore which could withstand both disk and host downtime, but we need to make that datastore available for consumption and also highly available in the process, for this we will use CTDB, as in the previous post. CTDB is a cluster version of the TDB database which sits under Samba. The majority of this section will be the same as the previous post except for the extra packages and a slightly different config for samba. Lets install the required packages:

yum -y install ctdb samba samba-common samba-winbind-clients samba-client samba-vfs-glusterfs

For the majority of config files we will create them in our shared config volume and symlink them to their expected location. First file we need to create is /etc/sysconfig/ctdb but we will do this as /opt/samba-config/ctdb then link it afterwards

Note: The files which are created in the shared area should be done only on one host, but the linking needs to be done on both.

vi /opt/samba-config/ctdb
 #CIFS only
 #CIFS only

We’ll need to remove the existing file in /etc/sysconfig then we can create the symlink

rm /etc/sysconfig/ctdb
ln -s /opt/samba-config/ctdb /etc/sysconfig/ctdb

Although we are using Samba the service we will be using is CTDB which allows for the extra clustering components, we need to stop and disable the samba services and enable the ctdb ones:

service smb stop
chkconfig smb off
chkconfig ctdb on

With this configuration being a cluster of essentially a single datapoint we should really use a single entry point, for this a 3rd “floating” or virtual IP address is employed, more than one could be used but lets keep this simple – We also need to create a ctdb config file which contains a list of all the nodes in the cluster. Both these files need to be created in the shared location:

vi /opt/samba-config/public_addresses eth0
vi /opt/samba-config/nodes

They both then need to be linked to their expected locations – neither of these exist so don’t need to be removed.

ln -s /opt/samba-config/nodes /etc/ctdb/nodes
ln -s /opt/samba-config/public_addresses /etc/ctdb/public_addresses

The last step is to modify the samba configuration to present the volume via cifs, I seemed to have issues using a linked file for samba so will only use the shared area for storing a copy of the config which can then be copied to both nodes to keep them identical.

cp /etc/samba/smb.conf /opt/samba-config/

Lets edit that file:

vi /opt/samba-config/smb.conf

Near the top add the following options

clustering = yes
idmap backend = tdb2
private dir = /opt/samba-config/

These turn the clustering (CTDB) features on and specify the shared directory where samba will create lockfiles. You can test starting ctdb at this point to ensure all is working, on both hosts:

cp /opt/samba-config/smb.conf /etc/samba/
service ctdb start

It should start OK, then health status of the cluster can be checked with

ctdb status

At this point I was finding that CTDB was not starting correctly, after a little bit of logwatching I found an error in the samba logs suggesting:

Failed to create pipe directory /run/samba/ncalrpc - No such file or directory

Also, to be search engine friendly the CTDB logfile was outputting

50.samba OUTPUT:ERROR: Samba tcp port 445 is not responding

This was a red herring, the port wasn’t responding as the samba part of CTDB wasn’t starting, 50.samba is a script in /etc/ctdb/events/ which actually starts the smb process.

So I created the directory /run/samba and restarted ctdb and the issue seems to have disappeared.

Now we have a started service, we can go ahead and add the configuration for the share. A regular samba share would look something like:

 comment = just a share
 path = /share
 read only = no
 guest ok = yes
 valid users = jon

In the previous post this would have been ideal if our gluster volume was mounted at share, but for this we are removing a layer and want samba to talk directly to gluster rather than via the fuse layer. This is achieved using a VFS object, we installed the samba-vfs-glusterfs package earlier. The configuration is slightly different within the smb.conf file also. Adding the following to our file should enable access to the share volume we created:

 comment = gluster vfs share
 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 = share

Notice the glusterfs: options near the bottom, these are specific to the glusterfs vfs object which is called further up (vfs objects = glusterfs). Another point to note is that the path is / this is relative to the volume rather than the filesystem, so a path to /test would be a test directory inside the gluster volume.

We can now reload the samba config, lets restart for completeness (on both nodes)

service ctdb restart

From a cifs client you should now be able to browse to \ (or whatever IP you specified as the floating IP).



All done!

To conclude, here we have created a highly resilient, highly available, very scalable storage solution using some fantastic technologies. We have created a single access method (Cifs on a floating  IP) to a datastore which is then stored on multiple hosts, which in turn store upon multiple disks. Talk about redundancy!

Useful links:


The post Gluster, CIFS, ZFS – kind of part 2 appeared first on Jon Archer.

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by on June 17, 2013

puppet lsi hardware raid module

In response to some discussion in the gluster community, I am releasing my puppet-lsi module. It’s quite simple, but it is very useful for rebuilding machines. It could do a lot more, but I wanted to depend on the proprietary LSI tools as little as possible. Running megacli with puppet would be a very doable hack, but I’m not sure enough devops out there who would use that feature.

Usage is straightforward if you like the sensible defaults:

include lsi::msm

The general idea is that you’ve probably already setup all your “virtual drive” RAID configurations initially, and now you’re deploying your setup using cobbler and puppet-gluster. This puppet-lsi module should install all the client side LSI tools, and make sure monitoring for the hardware RAID is working. Megacli and all the (evil?) vivaldi framework stuff will be up and running after puppet has run.

I haven’t tested this on a wide array of hardware, and there might even be newer LSI gear on the market. Please don’t test it on production servers. If you want help with this, you might have to sponsor some hardware, or send me somewhere where I can hack on some, because I don’t have a gluster test rig at the moment.

I am curious to hear what kind of RAID you’re using with gluster. Hardware? Software? Details rock. SGPIO with mdadm, and you’re my hero. I want to hear about that!

I hope this was useful to you, and in the meantime,

Happy hacking,


PS: The most useful feature of this module, is that it sets up monitoring of your RAID, and lets you access the management daemon through the now installed LSI services.