OVH Guide

FAQ

Les questions que vous pourriez vous poser.

What is Cloud Disk Array?

Cloud Disk Array (CDA) is a private, dedicated (on disk level) storage system powered by Ceph. During development and testing it was known as Ceph-as-a-Service. CDA gives you storage space that can be utilized in a number of ways:

  • RADOS (low-level Ceph-specific object storage) - when building a custom application that depends on Ceph
  • RBD (block devices) - can be used in dedicated servers with Linux or for VM disks in OpenStack and Proxmox environments
  • (soon) RGW (REST object storage) - can be used to build a CDN (with an OVH provided load-balancer)
  • (later) CephFS (NFS-like filesystem)
  • (later) NFS and CIFS (SAMBA) gateways for CephFS - for integration with existing Windows or Linux environments
  • (later) inter-DC replication

Our goal is to provide to customers all features of Ceph inside a service managed by OVH.

Where is my data stored?

Once you select a Data Center, your data will be replicated three times. Those replicas are placed on three different server machines on three different racks.

To reduce latency when accessing your cluster, your clients should be in the same OVH datacenter as your Ceph cluster.

Can I increase my Cloud Disk Array storage capacity?

This feature is not available yet. It will be within few days.

You will be able to increase the capacity from the manager.

Can I deploy a filesystem over my Cloud Disk Array? If yes which ones?

At the moment we do not provide yet CephFS. As an alternative for now you could build a NFS or SAMBA filesystem on top of RBD devices.

Can I decrease my Cloud Disk Array storage capacity?

No - at the moment it is not possible.

Is it possible to access a Cloud Disk Array from a service not hosted by OVH?

Short answer is: No - at the moment it is not possible.

Currently Cloud Disk Array provides only RBD (Rados Block Device) access to the data storage. The mechanism allows you to expose CDA as an ordinary Linux Block Device (e.g. /dev/rbd0).

In order to maximize performance and minimize latency for such block devices it is only possible to use RBD inside OVH network - from other OVH services. If you need external block device access please contact us.

Please keep in mind that there are plans to add another mechanism for accessing CDA data storage - Rados Gateway. Rados Gateway will be able to expose CDA access to services located outside OVH via SWIFT API.

Which OVH solutions are compatible with Cloud Disk Array?

Any solutions that can connect to the OVH local network.

Public Cloud, Dedicated Server, Private Cloud Computing (PCC), VPS.

How is ensured the High Availability of the Cloud Disk Array solution?

Cloud Disk Array is powered by Ceph, which is a storage solution with no single point of failure.

Whichever protocol you use to store your data in Ceph, it is stored internally as RADOS objects. Each object is replicated 3 times across 3 different servers in 3 different racks.

In case of 1 replica failure, there is no disruption for client (except for slight performance degradation because of recovery).

In case of 2 replica failures, client access is blocked to the degraded objects until they are replicated at least 2 times. This is done in order to prevent data loss.