18.7. Creating a file system DAX namespace on an NVDIMM

Procedure

1. List all namespaces on your system:

   # ndctl list --namespaces --idle
   [
     {
       "dev":"namespace1.0",
       "mode":"raw",
       "size":34359738368,
       "uuid":"ac951312-b312-4e76-9f15-6e00c8f2e6f4"
       "state":"disabled",
       "numa_node":1
     },
     {
       "dev":"namespace0.0",
       "mode":"raw",
       "size":38615912448,
       "uuid":"ff5a0a16-3495-4ce8-b86b-f0e3bd9d1817",
       "state":"disabled",
       "numa_node":0
     }
   ]

2. Reconfigure any namespace:

   # ndctl create-namespace --force --mode=fsdax --reconfig=namespace-ID

   例 18.2. Reconfiguring a namespace as file system DAX

   To use namespace0.0 for a file system that supports DAX, use the following command:

   # ndctl create-namespace --force --mode=fsdax --reconfig=namespace0.0
   {
     "dev":"namespace0.0",
     "mode":"fsdax",
     "map":"dev",
     "size":"11.81 GiB (12.68 GB)",
     "uuid":"f8153ee3-c52d-4c6e-bc1d-197f5be38483",
     "sector_size":512,
     "align":2097152,
     "blockdev":"pmem0"
   }

   The namespace is now available at the /dev/pmem0 path.

Procedure

1. List the pmem regions on your system that have available space. In the following example, space is available in the region1 and region0 regions:

   # ndctl list --regions
   [
     {
       "dev":"region1",
       "size":2156073582592,
       "align":16777216,
       "available_size":2117418876928,
       "max_available_extent":2117418876928,
       "type":"pmem",
       "iset_id":-9102197055295954944,
       "badblock_count":1,
       "persistence_domain":"memory_controller"
     },
     {
       "dev":"region0",
       "size":2156073582592,
       "align":16777216,
       "available_size":2143188680704,
       "max_available_extent":2143188680704,
       "type":"pmem",
       "iset_id":736272362787276936,
       "badblock_count":3,
       "persistence_domain":"memory_controller"
     }
   ]

2. Allocate one or more namespaces on any of the available regions:

   # ndctl create-namespace --mode=fsdax --region=regionN --size=namespace-size

   For example, the following command creates a 36-GiB file system DAX namespace on region0:

   # ndctl create-namespace --mode=fsdax --region=region0 --size=36G
   {
     "dev":"namespace0.3",
     "mode":"fsdax",
     "map":"dev",
     "size":"35.44 GiB (38.05 GB)",
     "uuid":"99e77865-42eb-4b82-9db6-c6bc9b3959c2",
     "sector_size":512,
     "align":2097152,
     "blockdev":"pmem0.3"
   }

   The namespace is now available as /dev/pmem0.3.

Procedure

1. Optional: Create a partition on the file system DAX device. For more information, see Creating a partition with parted.

   注意

   When creating partitions on an fsdax device, partitions must be aligned on page boundaries. On the Intel 64 and AMD64 architecture, at least 4 KiB alignment is required for the start and end of the partition. 2 MiB is the preferred alignment.

   By default, the parted tool aligns partitions on 1 MiB boundaries. For the first partition, specify 2 MiB as the start of the partition. If the size of the partition is a multiple of 2 MiB, all other partitions are also aligned.

2. Create an XFS or ext4 file system on the partition or the NVDIMM device:

   # mkfs.xfs -d su=2m,sw=1 fsdax-partition-or-device

   注意

   The dax-capable and reflinked files can now co-exist on the file system. However, for an individual file, dax and reflink are mutually exclusive.

   Also, to increase the likelihood of large page mappings, set the stripe unit and stripe width.

3. Mount the file system:

   # mount f_sdax-partition-or-device mount-point_

   There is no need to mount a file system with the dax option to enable direct access mode. When you do not specify any dax option while mounting, the file system is in the dax=inode mode. Set the dax option on the file before direct access mode is activated.