Cloud server volumes

Overview

We provide the Cloud Server Volumes service as an additional storage option to the Cloud Servers service of ours. The service allows for the persistent storage of data on volumes that can be attached to cloud servers as block storage devices. A physical hard drive is an example of a traditional block device; you can think of a block storage device as of a physical hard drive or USB stick, but more reliable.

High availability and durability

Each volume is triply replicated within its availability zone to protect data from component failure, offering high availability and durability. We use Ceph's RADOS Block Device (RBD) service to stripe and replicate data across the storage cluster automatically. We use OpenStack for our cloud computing service, hence OpenStack Cinder is used as an integration layer between Ceph and OpenStack.

Performance

We use solid-state drives (SSD) across our clustered storage. Physical SSD storage ensures high-speed data access. Triple replication of storage nodes guarantees high data availability and durability.

Limitations

- A single volume can only be attached to a single cloud server instance at a given time, but provides the flexibility to be detached from one instance and attached to another;

- Number of I/O operations per volume is capped at 9000/sec reads, 3000/sec writes;

- Bandwidth is capped at 375MB/sec read, 200MB/sec write;

- The Cloud Server Volumes service is available in selected locations.

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