Coho Data volume driver

Coho Data volume driver

The Coho DataStream Scale-Out Storage allows your Block Storage service to scale seamlessly. The architecture consists of commodity storage servers with SDN ToR switches. Leveraging an SDN OpenFlow controller allows you to scale storage horizontally, while avoiding storage and network bottlenecks by intelligent load-balancing and parallelized workloads. High-performance PCIe NVMe flash, paired with traditional hard disk drives (HDD) or solid-state drives (SSD), delivers low-latency performance even with highly mixed workloads in large scale environment.

Coho Data’s storage features include real-time instance level granularity performance and capacity reporting via API or UI, and single-IP storage endpoint access.

Supported operations

  • Create, delete, attach, detach, retype, clone, and extend volumes.
  • Create, list, and delete volume snapshots.
  • Create a volume from a snapshot.
  • Copy a volume to an image.
  • Copy an image to a volume.
  • Create a thin provisioned volume.
  • Get volume statistics.

Coho Data QoS support

QoS support for the Coho Data driver includes the ability to set the following capabilities in the OpenStack Block Storage API cinder.api.contrib.qos_specs_manage QoS specs extension module:

  • maxIOPS - The maximum number of IOPS allowed for this volume.
  • maxMBS - The maximum throughput allowed for this volume.

The QoS keys above must be created and associated with a volume type. For information about how to set the key-value pairs and associate them with a volume type, see the volume qos section in the OpenStackClient command list.


If you change a volume type with QoS to a new volume type without QoS, the QoS configuration settings will be removed.

System requirements

  • NFS client on the Block storage controller.

Coho Data Block Storage driver configuration

  1. Create cinder volume type.

    $ openstack volume type create coho-1
  2. Edit the OpenStack Block Storage service configuration file. The following sample, /etc/cinder/cinder.conf, configuration lists the relevant settings for a typical Block Storage service using a single Coho Data storage:

    enabled_backends = coho-1
    default_volume_type = coho-1
    volume_driver = cinder.volume.drivers.coho.CohoDriver
    volume_backend_name = coho-1
    nfs_shares_config = /etc/cinder/coho_shares
    nas_secure_file_operations = 'false'
  3. Add your list of Coho Datastream NFS addresses to the file you specified with the nfs_shares_config option. For example, if the value of this option was set to /etc/cinder/coho_shares, then:

    $ cat /etc/cinder/coho_shares
  4. Restart the cinder-volume service to enable Coho Data driver.

Description of Coho volume driver configuration options
Configuration option = Default value Description
coho_rpc_port = 2049 (Integer) RPC port to connect to Coho Data MicroArray
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