Ceph¶
Ceph is the storage system behind Sunet Cloud. A single Ceph cluster provides three kinds of storage, and most of the rest of the platform is built on top of it:
- Object storage (S3) is an S3-compatible API for storing and retrieving unstructured data such as backups, datasets, media, and application blobs. This is the storage you reach directly over the network from anywhere.
- Block storage (RBD) provides virtual disks. You do not use RBD directly; you consume it as OpenStack Cinder volumes attached to virtual machines, or as persistent volumes in a managed Kubernetes cluster.
- Filesystem (CephFS) is a shared POSIX filesystem that several clients can mount at once.
The same object store also backs Sunet Drive and provides the S3 endpoint exposed through OpenStack, so "Ceph S3", "OpenStack object storage", and the Drive storage backend are all the same underlying system.
Which storage do I want?¶
| What you need | Use |
|---|---|
| To store and fetch files over HTTP from scripts, apps, or backup tools | Object storage (S3) |
| A disk for a virtual machine | Block storage via OpenStack Cinder |
| A persistent volume for a container | Block storage via Kubernetes |
| A shared filesystem mounted by many VMs at once | Filesystem (CephFS) |
Durability and what is not backed up¶
Ceph keeps multiple copies (or erasure-coded shards) of your data across many disks and hosts, so it tolerates disk and node failures without losing data. Durability is not the same as backup. Ceph faithfully stores whatever you write, including an accidental delete or a file encrypted by ransomware. Sunet does not back up your object, block, or filesystem data by default, so plan your own backups. See Durability, quotas and billing for details.