File migration terminology

Table 1. File migration terminology
Term	Definition
File cluster	A set of File nodes that operate together. A File cluster can support a maximum of eight nodes. The first node by default operates as the Cluster controller and if the first node fails any node can take over Cluster controller activities .
NAS server	Network-attached storage (NAS) is a single point of access to a remote resource. Remote NDMP software may protect the file system data. Data may be stored on remote servers (offline DHSM files). Data may be protected against virus (virusChecker/CAVA (Common antivirus Agent)). A NAS server runs by default on his primary node. If the node crashes, the NAS server is moved to his backup node (failover).
Node	Node is the hosting platform for running PowerMax File in a docker-based container. Each node hosts Base Linux operating system, Docker services, and other necessary software to connect each PowerMax File container to replicated sites. There is one node running per Front-end director.
Primary Node	One of the File cluster nodes on which the NAS Server runs.
Backup Node	One of the PowerMax File cluster nodes, on which the NAS server is backed up for fault tolerance purposes. The NAS server is moved to this node during any failover event.
Client Interface	Network interface that is attached to the VDM (or NAS server) that is accessible by protocol clients, a.k.a. production interface. The interfaces that are taken over are all client interfaces.
Migration	As a tech refresh, migration is the transfer of eNAS1.0 VDM (source), both data and configuration, to a NAS server on PowerMax File (destination). After migration, the NAS service provider switches to the migrated server on destination. During the migration, the data layout has been changed from UFS32 in source to UFS64 in destination.
Initial Copy	Initial copy is the migration stage between migration start and cutover. It includes the provision of the migration object, that is, NAS server (VDM) and File Systems. Also included are the copy of the data from source to destination, and movement of the VDM configuration.
Cutover	The production NAS server is switched from source eNAS1.0 VDM to destination PowerMax NAS server. All user traffic is directed to the destination NAS server after cutover.
Incremental Copy (reverse)	After cutover, the migration progress must sync the uncopied and changed data during the baseline data copy from source to destination. This process is the so-called Incremental Copy stage of the migration cycle. During this stage, all writing operations against the migrated NAS on destination are synced back to the source. This sync ensures that the user change is not lost if there is a migration cancel.
Commit	Commit is the operation to complete a file migration. It can only occur when the data are 100% synced between source VDM and destination NAS server. After commitment, any data change is not synced back to the source again. The source VDM is offline.
Cold Files	Cold Files are files to be transferred in the Initial Copy phase. For a file system to be migrated during the Initial Copy phase, certain conditions must be met. The migration session only migrates files that are not expected to be modified throughout the entire Initial Copy phase. This migration is so that the most valuable data is transferred in Initial Copy. It is possible that some cold files are changed during its transfer; in that case, they are transferred again in the Incremental Copy phase. Those files with migration time smaller than "migration connection creation time - one hour" are defined as cold files.
Hot Files	Hot Files are on the opposite position of cold files, it is highly possible that these files are modified during the migration Initial Copy. The migration session does not transfer those files in the Initial Copy phase.
Inode	In a UNIX-style file system, the inode is a data structure that is used to represent a file system object. The object could be, for example, a file or a directory. Each inode stores the attributes and disk block locations of the data of the file system object.
Migration Interface	Network interfaces on the source or destination arrays that occur in pair for the migration engine to copy and sync data. Note: This interface is only for file migration purpose. Using it also in host I/O leads to data inconsistency between source and destination.
Non-disruptive Migration	The host (NAS client) should not be aware of the switch of the NAS server. No service interrupt occurs during the whole migration life cycle. To achieve that, the total DU time during cutover should be as small as 30 s (maximum 90 s).
Production Interface	See Client Interface above
Transparent Migration	See Non-Disruptive Migration above.
Active Migration	A migration session whose state is not Completed or Canceled.

File cluster

A set of File nodes that operate together. A File cluster can support a maximum of eight nodes. The first node by default operates as the Cluster controller and if the first node fails any node can take over Cluster controller activities .

NAS server

Network-attached storage (NAS) is a single point of access to a remote resource. Remote NDMP software may protect the file system data. Data may be stored on remote servers (offline DHSM files). Data may be protected against virus (virusChecker/CAVA (Common antivirus Agent)). A NAS server runs by default on his primary node. If the node crashes, the NAS server is moved to his backup node (failover).

Node

Node is the hosting platform for running PowerMax File in a docker-based container. Each node hosts Base Linux operating system, Docker services, and other necessary software to connect each PowerMax File container to replicated sites. There is one node running per Front-end director.

Primary Node

One of the File cluster nodes on which the NAS Server runs.

Backup Node

One of the PowerMax File cluster nodes, on which the NAS server is backed up for fault tolerance purposes. The NAS server is moved to this node during any failover event.

Client Interface

Network interface that is attached to the VDM (or NAS server) that is accessible by protocol clients, a.k.a. production interface. The interfaces that are taken over are all client interfaces.

Migration

As a tech refresh, migration is the transfer of eNAS1.0 VDM (source), both data and configuration, to a NAS server on PowerMax File (destination). After migration, the NAS service provider switches to the migrated server on destination. During the migration, the data layout has been changed from UFS32 in source to UFS64 in destination.

Initial Copy

Initial copy is the migration stage between migration start and cutover. It includes the provision of the migration object, that is, NAS server (VDM) and File Systems. Also included are the copy of the data from source to destination, and movement of the VDM configuration.

Cutover

The production NAS server is switched from source eNAS1.0 VDM to destination PowerMax NAS server. All user traffic is directed to the destination NAS server after cutover.

Incremental Copy (reverse)

After cutover, the migration progress must sync the uncopied and changed data during the baseline data copy from source to destination. This process is the so-called Incremental Copy stage of the migration cycle. During this stage, all writing operations against the migrated NAS on destination are synced back to the source. This sync ensures that the user change is not lost if there is a migration cancel.

Commit

Commit is the operation to complete a file migration. It can only occur when the data are 100% synced between source VDM and destination NAS server. After commitment, any data change is not synced back to the source again. The source VDM is offline.

Cold Files

Cold Files are files to be transferred in the Initial Copy phase. For a file system to be migrated during the Initial Copy phase, certain conditions must be met. The migration session only migrates files that are not expected to be modified throughout the entire Initial Copy phase. This migration is so that the most valuable data is transferred in Initial Copy. It is possible that some cold files are changed during its transfer; in that case, they are transferred again in the Incremental Copy phase. Those files with migration time smaller than "migration connection creation time - one hour" are defined as cold files.

Hot Files

Hot Files are on the opposite position of cold files, it is highly possible that these files are modified during the migration Initial Copy. The migration session does not transfer those files in the Initial Copy phase.

Inode

In a UNIX-style file system, the inode is a data structure that is used to represent a file system object. The object could be, for example, a file or a directory. Each inode stores the attributes and disk block locations of the data of the file system object.

Migration Interface

Network interfaces on the source or destination arrays that occur in pair for the migration engine to copy and sync data. Note: This interface is only for file migration purpose. Using it also in host I/O leads to data inconsistency between source and destination.

Non-disruptive Migration

The host (NAS client) should not be aware of the switch of the NAS server. No service interrupt occurs during the whole migration life cycle. To achieve that, the total DU time during cutover should be as small as 30 s (maximum 90 s).

Production Interface

See Client Interface above

Transparent Migration

See Non-Disruptive Migration above.

Active Migration

A migration session whose state is not Completed or Canceled.