Preparing your environment for use of extended count key data (ECKD) devices

If your GPFS cluster includes Linux® on Z instances, do not use virtual reserve/release.

Instead, follow the process that is described in Sharing DASD without Using Virtual Reserve/Release (https://www.ibm.com/docs/en/zvm/7.1?topic=sharing-dasd-without-using-virtual-reserverelease). Data integrity is handled by GPFS itself.

Preparing an ECKD device for GPFS

To prepare an ECKD device for GPFS, complete these steps on a single node:

Ensure that the ECKD device is online. To set it online, issue the following command:
```
chccwdev -e device_bus_id
```
Where device_bus_id identifies the device to be configured. device_bus_id is a device number with a leading 0.n, where n is the subchannel set ID. For example:
```
 chccwdev -e 0.0.3352
```
Low-level format the ECKD using one of the following commands.
Note: GPFS supports ECKD disks in either compatible disk layout (CDL) format or Linux disk layout (LDL) format. The DASD must be formatted with a block size of 4096.
- To specify CDL format, issue the following command:
```
 dasdfmt -d cdl device
```
  There is no need to specify a block size value, as the default value is 4096.
- To specify LDL format, issue the following command:
```
 dasdfmt -d ldl device
```
  There is no need to specify a block size value, as the default value is 4096.
In both of these commands, device is the node of the device. For example:
```
 dasdfmt -d cdl /dev/dasda
```
This step is for CDL disks only. It is an optional step because partitioning is optional for CDL disks.
If you want to partition the ECKD and create a single partition that spans the entire device, use the following command:
```
fdasd -a device
```
Note: This step is not required for LDL disks because the dasdfmt -d ldl command issued in the previous step automatically creates a single Linux partition on the disk.
If the ECKD device is shared with other cluster nodes, then it is a good idea to set the ECKD device offline and then back online on each node where the ECKD is shared. This procedure ensures that the updated partition information is spread among all shared nodes.

For more information about all of these commands, see the following:

Commands for Linux on Z topic in Device Drivers, Features, and Commands (https://www.ibm.com/docs/en/linux-on-systems?topic=configuration-device-drivers-features-commands) in the Linux on Z library overview.
Getting started with Elastic Storage for Linux on Z based on GPFS technology white paper, available on the Welcome Page for IBM Storage Scale in IBM® Documentation.

Repeat these steps for each ECKD to be used with GPFS.

After preparing the environment, set the ECKD devices online on the other nodes.

Note: After partitioning and formatting an ECKD device, the partition information is not distributed automatically to other cluster nodes. If the ECKD device is shared with different cluster nodes when they are online. It is recommended to set the ECKD device offline and then back online. This procedure updates the partition information for the specific ECKD device on the cluster node.

Always ensure that the ECKD devices are online before starting GPFS. To automatically set ECKD devices online at system start, see the documentation for your Linux distribution.