Externally migrated data

Backup Administration Guide for Hitachi NAS Platform

Version
15.1.x
Audience
anonymous
Part Number
MK-92HNAS007-29
Backup/restore of data sets that contain data migrated to external servers are affected by the following NDMP environment variables:
  • NDMP_BLUEARC_REMIGRATE
  • NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED
  • NDMP_BLUEARC_EXTERNAL_LINKS
  • The CLI command: migration-recreate-links-mode

Note that NDMP_BLUEARC_EXCLUDE_MIGRATED has no effect on externally migrated files.

Environment variable Default Setting Effect on backup Effect on restore
NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED n y Only externally migrated files are included in the backup data. Depends on NDMP_BLUEARC_EXTERNAL_LINKS/migration-recreate-links-mode.
n Normal files and externally migrated files are included in the backup data.

Depends on NDMP_BLUEARC_EXTERNAL_LINKS/migration-recreate-links-mode.

NDMP_BLUEARC_REMIGRATE y y Externally migrated files are marked as such in the backup data.

Depends on NDMP_BLUEARC_EXTERNAL_LINKS/migration-recreate-links-mode..

n Externally migrated files appear as normal files in the backup data.

Externally migrated files are converted to normal files.

NDMP_BLUEARC_EXTERNAL_LINKS remigrate ignore Externally migrated files are not included in the backup data. Externally migrated files cannot be restored.
recreate_link Only the metadata for the externally migrated file is included in the backup data. The recovery target file system is checked for a migration path. If a path exists, an external link is created (see the CLI migration-recreate-links-mode command). There is no restore of user data. If a migration path does not exist, a link is not created.
remigrate The metadata and user data of the externally migrated file are included in the backup data. The recovery target file system is checked for a migration path. If a path exists, an external link is created (see the CLI migration-recreate-links-mode command), and the user data is written to the external link. The user data is never written to the local file system. If a migration path does not exist, a normal file is created.
migration-recreate-links-mode test-before-recreate always-recreate-links No effect Creates a link. Does not check if the link is pointing at anything.
test-before-recreate No effect If an existing file (migrated or otherwise) exists, delete it, and then create a new link to the migration target and write the user data to it.
  • Note that in most cases, NDMP Data Management Applications automatically uses the environment variables that were specified on backup when restoring. It is recommended that you consider the desired restore behavior when specifying the backup variables. Other than in exceptional circumstances, use the same environment variables on restore as those specified at backup.
  • migration-recreate-links-mode is set per EVS and not per NDMP operation. It applies to restore only; therefore, it must be set on the EVS that hosts the recovery target file system.
  • Do not use NDMP_BLUEARC_EXTERNAL_LINKS = recreate_link with migration-recreate-links-mode = test-before-recreate. This configuration could lead to data loss.
  • When using NDMP_BLUEARC_EXTERNAL_LINKS = remigrate, the operation is unsuccessful if the migration path at restore is the same path as when the backup was made. This prevents accidental data loss when copying data between filesystems. It is therefore not possible to recover migrated data to the same filesystem that is the source of the backup using this method. An alternative is to restore to a different location (if no migration path is configured there, migrated files are converted to normal files) and then copy the data into the original location.
The settings to use for standard use cases are:
  • Only backup non-migrated data:
    • NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED = n
    • NDMP_BLUEARC_EXTERNAL_LINKS = ignore
    • Other variables are ignored
  • Only backup migrated data, automatically migrating on recovery:
    • NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED = y
    • NDMP_BLUEARC_REMIGRATE = y
    • NDMP_BLUEARC_EXTERNAL_LINKS = remigrate
    • migration-recreate-links-mode = test-before-recreate
  • Backup all data, automatically migrating data on recovery:
    • NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED = n
    • NDMP_BLUEARC_REMIGRATE = y
    • NDMP_BLUEARC_EXTERNAL_LINKS = remigrate
    • migration-recreate-links-mode = test-before-recreate
  • Backup non-migrated data, preserve links to migrated data (requires recovery of data at migration target by another mechanism):
    • NDMP_BLUEARC_INCLUDE_ONLY_MIGRATED = n
    • NDMP_BLUEARC_REMIGRATE = y
    • NDMP_BLUEARC_EXTERNAL_LINKS = recreate_link
    • migration-recreate-links-mode = always-recreate