Installation manual

Policy for Balancing Capacity
Migrations in a Multi-Protocol Namespace
CLI Storage-Management Guide 12-49
File-Attribute Migrations
The policies in this chapter migrate file attributes along with the files themselves. File
attributes are permission settings, the name or ID of the user who owns the file, the
group or groups who have access to the file, last-access times, named streams, and
other external data associated with the file. File-attribute migrations require special
semantics in a multi-protocol namespace (that is, a namespace whose shares support
both NFS and CIFS access). If your policies are set in a namespace that is NFS-only
or CIFS-only, you can skip this section.
A multi-protocol namespace can be backed by a heterogeneous mix of multi-protocol
filers (MPFs), possibly from multiple vendors. The ARX passes client requests to
these filers, and passes filer responses back to the clients. File attributes, such as file
ownership and permission settings, are managed by each filer.
NFS and CIFS have fundamentally different file attributes, and each MPF vendor has
unique semantics for reconciling the two. An NFS client can change a file’s attributes
on Filer X, and Filer X uses its semantics to change the CIFS attributes accordingly.
This translation is manifestly inexact, so an MPF from another vendor typically gets a
slightly different CIFS translation for the same NFS attributes.
If the ARX migrates the filer from Filer X to Filer Y (made by two different vendors),
it takes these different semantics into account. This ensures that the NFS and CIFS
file attributes are preserved as much as possible as they are migrated from one vendor
to another. In some cases, file attributes are interpreted differently on the destination
filer. The sections below share the details of attribute migration.
Use these tables along with vendor documentation to determine any implications for
your clients.