Using multiple HDP pools

Storage Subsystem Administration Guide for Hitachi NAS Platform

Part Number

When you create or expand a filesystem, the server must find free chunks of disk space. If the span resides on two or more stripesets - that is, if the span has been expanded - then the server must select a stripeset to provide the space for each new chunk. If both stripesets' SDs are virtualizations of LUs on the same remote HDP pool, the server can select either stripeset with equal safety. However, if there are two or more remote HDP pools and they have different amounts of free space, the server has no way to tell which stripeset is the safest. That decision needs to be made by the Administrator.

In NAS Manager, if the server cannot select the stripeset, the Expand File System page shows a list of stripesets from which to select.

Through the command line, if a UVM-based span resides on two or more thinly provisioned remote HDP pools, the person provisioning the system must run the span-uvm-thin-provisioning command to warn the server. Each time a file system is expanded, the server will require the Administrator to select a stripeset using the filesystem-expand --on-stripeset command.

The person provisioning the system must run the span-uvm-thin-provisioning command once for each span that is in this configuration.

There is no filesystem-create --on-stripeset switch. Therefore, when a new filesystem is required, the administrator needs to:

  • Check that all HDP pools contributing space to the span have enough space.
  • Create the smallest possible filesystem.
  • Use the filesystem-expand --on-stripeset command to expand it onto a stripeset that has enough disk space.