Ceph
We offer Ceph as a scalable and fast way to obtain storage for your needs.
How does it work?
The gist how Ceph works for you:
We have many servers with SSDs or HDDs, each bought by one organization unit such as a chair. Data is spread accross all servers, and each organization unit gets as much storage space as they bought in servers.
You can access the storage mainly via RBD (RADOS block device), which is a device behaving like a local disk (USB stick, SSD, ...), but actually stores and retrieves data from the cluster in our data centre.
RBD acquisition
An RBD is a storage device you can use in your servers to store data in our Ceph cluster. It either uses HDD or SSD storage (cheaper vs faster).
For evaluation purposes, you can get small amounts of storage directly.
Otherwise, you can get as much space as you are entitled to.
Each RBD is stored in a "namespace", which restricts access to it. You can have multiple RBDs in the same namespace.
The name of an RBD is ORG-name/namespacename/rbdname.
To request the creation (or extension) of an RBD, write to support@ito.cit.tum.de specifying name, size, namespace and HDD/SSD.
You will get back a secret keyring to access the namespace.
RBD mapping
In order to "use" an RBD in your server, you need to "map" it.
You should have ready the name and keyring of the RBD.
- Please install ceph-common, at least in version 15.
- It contains a tool named rbdmap, which can (oh wonder) map your RBD.
- Edit /etc/ceph/rbdmap to add your RBD in a line
- it has the format: rbdname name=keyringname,options=...
- ORG-name/namespacename/rbdname name=client.ORG.rbd.namespacename,options='queue_depth=1024'
- Place the keyring file in /etc/ceph/
- Filename: ceph.client.ORG.rbd.namespacename.keyring
- Permissions: 700
- Owner: root
- Content: the client identifier and 28 byte key in base64 encoding.
- [client.ORG.rbd.namespacename]
key = ASD+OdlsdoTQJxFFljfCDEf/ASDFlYIbEbZatg==
RBD formatting
Now that you have mapped your RBD, we can create file system structures on it.