Deleting disks from a file system

Start of changeBefore you delete a disk from an IBM Storage Scale file system, use the mmdf command to determine whether the file system has sufficient free space to accommodate all data or metadata in the storage pool where the disk is located.End of change

  • See Querying file system space for more information about diagnosing space problems.
  • For file systems where the majority of files are smaller than the file system block size, resulting in fragmentation of storage space, it is recommended that the free space in the file system be at least 150 percent of the space consumed by the disks that will be deleted. For example, to delete a 400 GB disk from a file system, you must first confirm that the file system contains minimum 600 GB of free space in the storage pool from where the disk is being removed.
    Note: Rebalancing of files is an I/O intensive and time consuming operation, and is important only for file systems with large files that are mostly invariant. In many cases, normal file update and creation rebalance your file system over time, without the cost of the rebalancing.
  • A disk that is being deleted must be in an accessible state, that is started or suspended, to allow for data to be moved off of the disk to another disk in the storage pool. If a disk is being removed because it is damaged or is no longer working, then additional precautions are necessary before the disk is deleted from the file system. Deleting a disk that is no longer accessible can cause a loss of data, and if the disk contains metadata, you may need to run the mmfsck command. For further information about removing damaged or inaccessible disk see NSD and underlying disk subsystem failures and Disk media failure.

Start of changeWhen you need to remove or replace one or more disks in a file system, you can use the mmrestripefs command. Because this command is tolerant to stop and restart, you can control the process of moving data off of one or more disks that are being removed or replaced. You can also use the quality of service (QoS) feature (the mmqos command) to control the impact of the I/Os necessary to move data from one or more disks that are being removed or replaced to other disks.End of change

To use the mmrestripefs command before the removal or replacement of a disk complete the following steps:

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  1. Confirm that there is sufficient free space in the storage pool where the disk is located.
  2. Suspend the disks that need to be removed or replaced by using the mmchdisk command.
  3. Use the mmrestripefs command to move all data from the suspended disks.
  4. Use the mmdeldisk command to remove one or more disks, or use the mmrpldisk command to replace one or more disks.

    For syntax and usage information, refer to mmdeldisk command.

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