1.2.20.2 Volume Attachments

To use a block volume, you must create a volume attachment. There are two types of volume attachment:

• An Exascale Direct Volume (EDV) attachment creates a association between the volume and an EDV device file on the Exadata compute node or Oracle Grid Infrastructure (GI) cluster hosting the attachment.

  If you create a cluster-wide attachment, the EDV device file is created on every node in the GI cluster. If you create a node-specific attachment, the corresponding EDV device is only created on that node.

  After attachment, the volume can be used as a raw block storage device or to support a file system. To implement Oracle Advanced Cluster File System (ACFS) on Exascale block volume storage, you must use an EDV attachment.

  The I/O for each attachment is serviced by an EDV server process. Automatic data encryption and decryption occurs within the EDV process.

  EDV is the default and recommended volume attachment type for cases where clients want to use volumes within the Exadata RDMA Network Fabric. In addition to general file storage, an EDV attachment may be used to support Oracle Database data files for versions before Oracle Database 23ai. However, an EDV attachment cannot be used for a bootable volume.

• An iSCSI attachment enables the volume to be used as an iSCSI target.

  Attachments of this kind create a association between the volume (iSCSI target) and an iSCSI initiator. After attachment, the iSCSI initiator can use standard iSCSI protocols and commands to interact with the target (volume).

  The I/O for each attachment is serviced by a block store worker (BSW) process that provides a reliable network endpoint by using a block store virtual IP address (VIP).

  Exascale supports mutual CHAP (Challenge Handshake Authentication Protocol) for authentication of iSCSI initiators. Data passing through an iSCSI volume attachment is automatically encrypted and decrypted inside the block store worker process.

  An Exascale iSCSI attachment may be used to support a bootable volume.

After you create the first attachment for a volume, the volume is marked and can only be attached using the same type of volume attachment.

Regardless of attachment type, Exascale supports the simultaneous use of multiple attachments for each volume, which can be used to support various types of clustered file systems.