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1	1	We offer [Ceph](https://ceph.io) as a scalable and fast way to obtain storage for your needs.
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	3	+{{toc/}}
	4	+
	5	+## How does it work?
	6	+
	7	+The gist how Ceph works for you:
	8	+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.
	9	+
	10	+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.
	11	+
	12	+## RBD acquisition
	13	+
	14	+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).
	15	+
	16	+For evaluation purposes, you can get small amounts of storage directly.
	17	+Otherwise, you can get as much space as you are entitled to.
	18	+
	19	+Each RBD is stored in a "namespace", which **restricts access** to it. You can have multiple RBDs in the same namespace.
	20	+
	21	+The name of an RBD is `ORG-name/namespacename/rbdname.`
	22	+
	23	+To request the creation (or extension) of an RBD, write to [[support@ito.cit.tum.de|mailto:support@ito.cit.tum.de]] specifying **name**, **size**, **namespace** and **HDD/SSD**.
	24	+
	25	+You will get back a secret **keyring** to access the namespace.
	26	+
	27	+## RBD mapping
	28	+
	29	+In order to "use" an RBD in your server, you need to "map" it.
	30	+
	31	+You should have ready the name and keyring of the RBD.
	32	+
	33	+* Please install `ceph-common`, at least in version 15.
	34	+ * It contains a tool named `rbdmap`, which can (oh wonder) map your RBD.
	35	+* Edit /etc/ceph/rbdmap to add your RBD in a line
	36	+ * it has the format: `rbdname name=keyringname,options=...`
	37	+ * `ORG-name/namespacename/rbdname name=client.ORG.rbd.namespacename,options='queue_depth=1024'`
	38	+* Place the keyring file in /etc/ceph/
	39	+ * Filename: `ceph.client.ORG.rbd.namespacename.keyring`
	40	+ * Permissions: 700
	41	+ * Owner: root
	42	+ * Content: the client identifier and 28 byte key in base64 encoding.
	43	+ * [client.ORG.rbd.namespacename]
	44	+ key = ASD+OdlsdoTQJxFFljfCDEf/ASDFlYIbEbZatg==
	45	+
	46	+## RBD formatting
	47	+
	48	+Now that you have mapped your RBD, we can create file system structures on it.