Configuring PMEM Devices

On your Intel Persistent Memory (PMEM) device, use the ipmctl utility to configure the PMEM mode and the ndctl utility for namespace management.

A PMEM device can operate in App Direct mode, Memory Mode, or Mixed Mode. To use OMS, you should configure your PMEM device in the app direct mode by using the BIOS.

In your BIOS, select EDKII, Socket Config, Memory Config, Memory Map, Volatile Mode and set it to 1LM.
Log in as root and check the currently configured capacity:
```
$ su -
# ipmctl show -memoryresources
```
The output is similar to the following:
```
Capacity=3029.4 GiB
MemoryCapacity=0.0 GiB
AppDirectCapacity=3024.0 GiB
UnconfiguredCapacity=0.0 GiB
InaccessibleCapacity=5.4 GiB
ReservedCapacity=0.0 GiB
```
In this example, the system has an aggregate capacity of 3024 GiB (3247 GB).

Note:
A GiB (gibibyte) is a unit of measure that represents 1024 MiB (mebibytes), equivalent to 2³⁰ bytes.

Verify if the regions are configured in app direct mode.

# ipmctl show -region

The output is similar to the following:

SocketID | ISetID             | PersistentMemoryType | Capacity  | FreeCapacity | HealthState
===============================================================================================
0x0000   | 0x97407f48df982ccc | AppDirect            | 1512.0 GiB | 0.0 GiB      | Healthy
0x0001   | 0xfb907f48d59a2ccc | AppDirect            | 1512.0 GiB | 0.0 GiB      | Healthy

In this example, there are two PMEM devices; one per socket. Each PMEM device or region has a capacity of 1512 GiB and supports AppDirect mode.

Create the namespace by running the ndctl command for each region. In this example, run the command twice as there are two regions in the preceding example.
```
# ndctl create-namespace
# ndctl create-namespace
```

Check if the namespaces are created.

# ndctl list -u

The output is similar to the following:

[
  {
    "dev":"namespace1.0",
    "mode":"fsdax",
    "map":"dev",
    "size":"1488.37 GiB (1598.13 GB)",
    "uuid":"f8ec094d-5a69-4f87-9198-fb9117f2ea8e",
    "sector_size":512,
    "align":2097152,
    "blockdev":"pmem1"
  },
  {
    "dev":"namespace0.0",
    "mode":"fsdax",
    "map":"dev",
    "size":"1488.37 GiB (1598.13 GB)",
    "uuid":"8924aa35-701f-40cc-ba08-654aa5729611",
    "sector_size":512,
    "align":2097152,
    "blockdev":"pmem0"
  }
]

In this example, two namespaces namespace0.0 and namespace1.0 are now available for NUMA nodes 0 and node 1 respectively. The block device paths for namespaces namespace0.0 and namespace1.0 are /dev/pmem0 and /dev/pmem1 respectively.

Ensure that the PMEM device starts at a 2 MiB aligned physical address.
To determine the alignment of the persistent memory namespaces, view the /proc/iomem file.
```
# cat /proc/iomem | grep namespace
  3060000000-1aa5fffffff : namespace0.0
  1da00000000-353ffffffff : namespace1.0
```
Check if the hexadecimal addresses are aligned at a 2 MiB boundary.
```
0x3060000000 = 198144 MiB

0x1da00000000 = 1941504 MiB
```
In this example, both addresses are aligned at a 2 MiB boundary.
Create two partitions on your PMEM storage device. One small partition of approximately 5 percent for metadata and the rest for the data.

On /dev/pmem0 create 2 partitions pmem0p1 and pmem0p2.

Here pmem0p1 is the smaller metadata partition and pmem0p2 is the larger data partition.

In the following example, 5 percent of the total space of 1488.37 GiB would be approximately 75 GiB. Partition the device as follows:
1. Launch parted and select the device.
```
# parted /dev/pmem0

GNU Parted 3.2
Using /dev/pmem0
Welcome to GNU Parted! Type 'help' to view a list of commands.
```
2. Create the first new 75 GiB partition using the mkpart command.
```
(parted) mkpart
Partition type? primary/extended? p
File system type? [ext2]? xfs
Start? 2MiB
End? 75GiB
```
3. Create the second new partition using the mkpart command.
```
(parted) mkpart
Partition type? primary/extended? p
File system type? [ext2]? xfs
Start? 75GiB
End? -2MiB
```
4. Quit parted and return to the shell prompt.
```
(parted) q
Information: You may need to update /etc/fstab.
```
  Similarly, partition the /dev/pmem1 device.

Ensure that you align the starting sector of the data partition at 2 MiB.

The starting sector number of the data partition should be a multiple of 4096 when you run the fdisk -l command.

Run the fdisk -l command on /dev/pmem0 and /dev/pmem1 to check if the sector is aligned properly.

# fdisk -l /dev/pmem0

Disk /dev/pmem1: 1598.1 GB, 1598128390144 bytes, 3121344512 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0xc1d8d265

      Device Boot      Start         End      Blocks   Id  System
/dev/pmem0p1            4096   157286399    78641152   83  Linux
/dev/pmem0p2       157286400  3121340415  1482027008   83  Linux

# fdisk -l /dev/pmem1

Disk /dev/pmem1: 1598.1 GB, 1598128390144 bytes, 3121344512 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x0003b5eb

      Device Boot      Start         End      Blocks   Id  System
/dev/pmem1p1            4096   157286399    78641152   83  Linux
/dev/pmem1p2       157286400  3121340415  1482027008   83  Linux

In these examples the starting sector of the data partitions are multiples of 4096, which confirms that the data partition is aligned at 2 MiB.

157286400 / 4096 = 38400

Parent topic: Setting-Up Hardware and Operating System Components for OMS