[DRBD-user] Some question about linstor

[Robert Altnoeder]

Hello,

On 02/22/2018 11:35 AM, yang zhenyu wrote:
> [...]
>
> The following is my understanding:
>
> 1. The LINSTOR Controller node corresponds to the drbdmanage pure
> controller, there is no storage.
> 2. The LINSTOR Combined node corresponds to the drbdmanage controller
> with storage.
> 3. The LINSTOR Satellites node  corresponds to the drbdmanage
> satellites with storage.

LINSTOR comprises two modules, the controller and the satellite.

Only the controller manages the configuration, e.g., all resource
definitions, storage pools, network interfaces of nodes, etc. are
defined on the controller.

Only the satellites deal with actual storage, with DRBD, etc., and the
satellites obtain information about the configuration of their resources
from the active controller (the controller contacts all registered
satellites).

Only one controller is active at a time, but multiple installations of
the controller may be provided so that if the active controller node
crashes, the controller can be started on another node. This kind of
failover is managed by a cluster manager such as Pacemaker.

A combined node is a node that can run the controller module and the
satellite module. This is required if one of the storage nodes is also
running the controller module. In this case, the controller module and
the satellite module will be running on that node at the same time, and
the controller will connect to the satellite on the local node the same
way it connects to remote satellites.

The controller can also be installed on platforms that do not support
the kind of storage that the satellites support, or that do not support
DRBD (e.g., you could run the controller on an AIX or HP/UX box and have
it control satellites that run on Linux, and in the future also Windows
with DRBD for Windows).

> 4. The LINSTOR Auxiliary node corresponds to the drbdmanage client node?

Auxiliary nodes are more or less disabled nodes, they do not run the
LINSTOR software. They are needed for future features, as of now, they
are not very useful for anything.

> 5. Only the control node to access the database?

Only one controller is connected to the database at any time.

> Currently linstor only use the derby database? So I need a shared storage for multiple
> control nodes.

Technically, the controller is able to connect to a
centralized/networked database (we run one of our development systems
with such a configuration), but normally it runs an Apache Derby
embedded database in the controller module's process. The database layer
is exchangable, but Derby is the only driver that is implemented as of
today.

> But I do not understand what is the ues of cluster manage software at here? For example pacemaker.

It can be used for automatic failover to another controller if the
active controller node fails.

best regards,
-- 
Robert Altnoeder
+43 1 817 82 92 0
robert.altnoeder at linbit.com

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