Configuration considerations when using HDP with NAS

Storage Subsystem Administration Guide for Hitachi NAS Platform

Part Number

When your system must work with HDP-based storage, there are things to remember that affect both the storage and the NAS server. For detailed information on using HDP with your particular storage, consult the HDP software documentation.

When using HDP pools with NAS servers, consider the following:
  • All current Hitachi Vantara storage supports HDP as a licensed option.
  • All NAS servers support HDP without requiring a server-side license.
  • The HDP software has no effect on protocol clients, such as NFS, and SMB.
  • Each DP-Vol draws space from multiple pool volumes, which helps to relieve the storage bottleneck by distributing I/O to more disks.
  • If you attempt to create or expand a file system and either there are not enough free chunks on the span or there is not enough free disk space on the DP pool, the server will make space by recycling one or more deleted file systems, if the span contains any.
    Note: When you recycle or delete a file system, the amount of free space shown in a storage configurator such as Hitachi Ops Center Administrator or Hitachi Storage Navigator does not reflect the new space until after you have run the span-unmap-vacated-chunks command. Do not run this command unnecessarily because performance may be reduced.
  • Recycling a file system causes the chunks that stored the file system data to be moved into the vacated-chunks list, which contains records of which freed chunks were used by which file system.
  • Creating or expanding a file system draws space from the vacated chunks list, if any is available, without using new space from the HDP pool. Any further space is pre-allocated at once.
  • Writing to a file system costs no space because that space was pre-allocated.
  • When creating or expanding a storage pool on HDP pools, you must use the DP-Vols from a single DP pool. This rule applies whether you are using the CLI or the NAS Manager. Later storage pool expansions can be done using storage from different DP pools.