3.9.2.1.1 Create an EDV Attachment

To use a volume, you must create a volume attachment. An Exascale Direct Volume (EDV) attachment 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.

Note:

During initial system deployment with Oracle Exadata Deployment Assistant (OEDA), the Exascale Direct Volume (EDV) service is configured on each Exadata compute node (bare-metal or VM) and is related to the Exascale user that manages the Oracle Grid Infrastructure (GI) cluster. To create an EDV attachment, you must use the Exascale user linked with the EDV service.

If the GI cluster uses a non-role-separated user configuration with one Oracle OS user account, then the associated Exascale user is related to the EDV service. If the GI cluster uses a role-separated configuration with a Grid OS user account and an Oracle OS user account, then the EDV service is linked to the Exascale user associated with the Grid OS account.

To find the Exascale user linked with the EDV service, use the ESCLI lsinitiator command with the --detail option and examine the user attribute.

To create an EDV attachment, connect to ESCLI as the Exascale user linked with the EDV service. Then, run the mkvolumeattachment command and specify:

  • The volume identifier. You can use the lsvolume command to find the identifier for each volume.

  • The device name to use in conjunction with the attachment. This is a user-supplied name, which is applied to the device file that is associated with the attachment. After attachment, the corresponding device file is located under /dev/exc/.

  • The cluster identifier (giClusterId) or specific EDV initiator identifier (initiator) where the attachment resides. You can use the lsinitiator command to find cluster and EDV initiator identifiers.

    If you create a cluster-wide attachment, the EDV device file is created on every node in the Oracle Grid Infrastructure (GI) cluster. If you create a node-specific attachment, the corresponding EDV device file is only created on the node associated with the specified EDV initiator.

For example, the following command creates a node-specific EDV attachment:

@> mkvolumeattachment 1:8e4fbaff261440b493e0a5e5e6808e66 myvol --attributes initiator=1fd9b363-079a-84e2-1fd9-b363079a84e2

In the example:

  • The volume identifier is 1:8e4fbaff261440b493e0a5e5e6808e66.

  • The device name to use in conjunction with the attachment is myvol, and the corresponding device file is located at /dev/exc/myvol.

  • The EDV initiator identifier is 1fd9b363-079a-84e2-1fd9-b363079a84e2. This value identifies a specific cluster node (server) that hosts the EDV attachment.

Note:

  • Each EDV attachment also has a kernel device file at /dev/exc-devN, where N is the minor number of the device. The kernel device name is contained as an attribute of the EDV attachment and is visible using the ESCLI lsvolumeattachment command. The relationship between the kernel device file and the user-named device file (under /dev/exc/) is also recorded in the udev database and is visible using the following Linux command: 

    # udevadm info device-file

    For the device-file value, you can specify either the kernel device file (/dev/exc-devN) or the user-named device file (under /dev/exc/).

  • By default, read and write access to EDV device files is only available to the root operating system user and members of the disk group. Depending on your use case, you may need to modify the permissions on the EDV device files before using them.

    For example, to make the EDV device file at /dev/exc/myvol readable and writable by the oracle user and dba group, you could configure it using a udev rule similar to the following: 

    # cat /etc/udev/rules.d/57-edv-user.rules
KERNEL=="exc-*", ENV{EXC_ALIAS}=="myvol", OWNER="oracle", GROUP="dba", MODE="0660"

  • To facilitate the management of udev rules related to EDV devices, each EDV client node is configured with a template udev rules file at /etc/udev/rules.d/57-edv-user.rules, which you can modify to fulfill your requirements. To maintain existing udev rules, /etc/udev/rules.d/57-edv-user.rules is preserved whenever the EDV client software is updated.

  • Each EDV client node can support a maximum of 1024 attachments at the same time. This limit includes the total of all cluster attachments involving the server, as well as local attachments specific to the server.

  • For simple cases, you can streamline the creation of an Exascale volume and associated Exascale Direct Volume (EDV) attachment by using the edvmkvol command.

Parent topic: Administer EDV Attachments