Configuring the iSCSI Target using Ansible¶
The Ceph iSCSI gateway is the iSCSI target node and also a Ceph client node. The Ceph iSCSI gateway can be provisioned on dedicated node or be colocated on a Ceph Object Store Disk (OSD) node. The following steps will install and configure the Ceph iSCSI gateway for basic operation.
Requirements:
A running Ceph Luminous (12.2.x) cluster or newer
Red Hat Enterprise Linux/CentOS 7.5 (or newer); Linux kernel v4.16 (or newer)
The
ceph-iscsi
package installed on all the iSCSI gateway nodes
Installation:
On the Ansible installer node, which could be either the administration node or a dedicated deployment node, perform the following steps:
As
root
, install theceph-ansible
package:# yum install ceph-ansible
Add an entry in
/etc/ansible/hosts
file for the gateway group:[iscsigws] ceph-igw-1 ceph-igw-2
Note
If co-locating the iSCSI gateway with an OSD node, then add the OSD node to the
[iscsigws]
section.
Configuration:
The ceph-ansible
package places a file in the /usr/share/ceph-ansible/group_vars/
directory called iscsigws.yml.sample
. Create a copy of this sample file named
iscsigws.yml
. Review the following Ansible variables and descriptions,
and update accordingly. See the iscsigws.yml.sample
for a full list of
advanced variables.
Variable |
Meaning/Purpose |
---|---|
|
Each gateway needs access to the
ceph cluster for rados and rbd
calls. This means the iSCSI gateway
must have an appropriate
|
|
Define a custom storage cluster name. |
|
Define a custom keyring name. |
|
If set to |
|
This is a boolean value that checks for multipath and lvm configuration settings on each gateway. It must be set to true for at least the first run to ensure multipathd and lvm are configured properly. |
|
The user name for the API. The default is admin. |
|
The password for using the API. The default is admin. |
|
The TCP port number for using the API. The default is 5000. |
|
True if TLS must be used. The default is false. If true the user must create the necessary certificate and key files. See the gwcli man file for details. |
|
A list of IPv4 or IPv6 addresses who have access to the API. By default, only the iSCSI gateway nodes have access. |
Deployment:
Perform the followint steps on the Ansible installer node.
As
root
, execute the Ansible playbook:# cd /usr/share/ceph-ansible # ansible-playbook site.yml --limit iscsigws
Note
The Ansible playbook will handle RPM dependencies, setting up daemons, and installing gwcli so it can be used to create iSCSI targets and export RBD images as LUNs. In past versions,
iscsigws.yml
could define the iSCSI target and other objects like clients, images and LUNs, but this is no longer supported.Verify the configuration from an iSCSI gateway node:
# gwcli ls
Note
See the Configuring the iSCSI Target using the Command Line Interface section to create gateways, LUNs, and clients using the gwcli tool.
Important
Attempting to use the
targetcli
tool to change the configuration will cause problems including ALUA misconfiguration and path failover issues. There is the potential to corrupt data, to have mismatched configuration across iSCSI gateways, and to have mismatched WWN information, leading to client multipath problems.
Service Management:
The ceph-iscsi
package installs the configuration management
logic and a Systemd service called rbd-target-api
. When the Systemd
service is enabled, the rbd-target-api
will start at boot time and
will restore the Linux IO state. The Ansible playbook disables the
target service during the deployment. Below are the outcomes of when
interacting with the rbd-target-api
Systemd service.
# systemctl <start|stop|restart|reload> rbd-target-api
reload
A reload request will force
rbd-target-api
to reread the configuration and apply it to the current running environment. This is normally not required, since changes are deployed in parallel from Ansible to all iSCSI gateway nodesstop
A stop request will close the gateway’s portal interfaces, dropping connections to clients and wipe the current LIO configuration from the kernel. This returns the iSCSI gateway to a clean state. When clients are disconnected, active I/O is rescheduled to the other iSCSI gateways by the client side multipathing layer.
Removing the Configuration:
The ceph-ansible
package provides an Ansible playbook to
remove the iSCSI gateway configuration and related RBD images. The
Ansible playbook is /usr/share/ceph-ansible/purge_gateways.yml
. When
this Ansible playbook is ran a prompted for the type of purge to
perform:
lio :
In this mode the LIO configuration is purged on all iSCSI gateways that are defined. Disks that were created are left untouched within the Ceph storage cluster.
all :
When all
is chosen, the LIO configuration is removed together with
all RBD images that were defined within the iSCSI gateway
environment, other unrelated RBD images will not be removed. Ensure the
correct mode is chosen, this operation will delete data.
Warning
A purge operation is destructive action against your iSCSI gateway environment.
Warning
A purge operation will fail, if RBD images have snapshots or clones and are exported through the Ceph iSCSI gateway.
[root@rh7-iscsi-client ceph-ansible]# ansible-playbook purge_gateways.yml
Which configuration elements should be purged? (all, lio or abort) [abort]: all
PLAY [Confirm removal of the iSCSI gateway configuration] *********************
GATHERING FACTS ***************************************************************
ok: [localhost]
TASK: [Exit playbook if user aborted the purge] *******************************
skipping: [localhost]
TASK: [set_fact ] *************************************************************
ok: [localhost]
PLAY [Removing the gateway configuration] *************************************
GATHERING FACTS ***************************************************************
ok: [ceph-igw-1]
ok: [ceph-igw-2]
TASK: [igw_purge | purging the gateway configuration] *************************
changed: [ceph-igw-1]
changed: [ceph-igw-2]
TASK: [igw_purge | deleting configured rbd devices] ***************************
changed: [ceph-igw-1]
changed: [ceph-igw-2]
PLAY RECAP ********************************************************************
ceph-igw-1 : ok=3 changed=2 unreachable=0 failed=0
ceph-igw-2 : ok=3 changed=2 unreachable=0 failed=0
localhost : ok=2 changed=0 unreachable=0 failed=0