Method and system for migrating data while maintaining hard links

1. A computer implemented method of migrating all data from at least one original host storage system to a replacement host storage system, comprising:

connecting a replacement host storage system to an original host storage system;

retrieving attributes of a remote file having data to be migrated from the original host storage system to the replacement host storage system, and storing the attributes in a database migration database in the replacement host storage system;

determining if data in the remote file is linked to one file or to more than one file, if the data in the remote file is linked to only one file, creating a file in the replacement host storage system and migrating the data thereto;

if the data in the remote file is linked to more than one file, wherein said more than one file is two files, retrieving a file id and file system id from the retrieved attributes in a replacement host storage system data migration database, determining if the file id and file system id for the more than one file which the remote file is linked with are found in the replacement host storage system data migration database, if the file id and file system id for the more than one file are found in the replacement host storage system data migration database, retrieving a replacement host storage system id for the more than one file and creating a hard link to the more than one file associated with the file system id retrieved, and if the file id and file system id are not found in the replacement host storage system data migration database, creating a new file in the replacement host storage system, retrieving a file id from the original host storage system for the newly created file in the replacement storage system file system, migrating the data associated therewith from the original host storage system to the replacement host storage system, and storing the retrieved file id for the file in the data migration database keyed by the file id and file system id retrieved from the file attributes from the original host storage system, in the replacement host storage system;

if the data in the remote file is linked to more than two files, linking a file id and file system id for each other file to which it is linked from the retrieved attributes in the replacement host storage system, determining if a file id and file system id for each file is found in the data migration database in the replacement host storage system, for each other file id and file system id found in the data migration database in the replacement host storage system, retrieving a replacement host storage system id for each other file and creating a hard link to each, and for each other file whose file id and file system id is not found in the replacement host storage system data migration database, creating for each a new file in the replacement host storage system, retrieving a file id for each newly created file in the replacement storage file system from the original host storage system, migrating associated therewith from the original host storage system to the replacement host storage system, storing the retrieved file id for the file in the data migration database in the replacement host storage system keyed by the file id and file system id retrieved from the file attributes from the original host storage system, and creating a hard link to each other file; and

conducting the method for all data in the original host storage system wherein all data in the original host storage system is migrated to the replacement host storage system.

2. The method of claim 1 , further comprising creating hard links between files whose file id and file system id are found in the data migration database and files in the replacement host storage system for which data is migrated from the original host storage system, for all files associated with the same data.

3. A replacement host storage system for migrating all data from an original host storage system to the replacement host storage system, the replacement host storage system, comprising:

means for connecting the replacement host storage system directly to an original host storage system from which data is to be copied onto the replacement host storage system;

a file system module for arranging and managing data on the replacement host storage system; and

a data migration module for retrieving attributes of a remote file in the original host storage system having data to be migrated from the original host storage system to the replacement host storage system, and said file system module further comprising a data migration database in the replacement host storage system for storing the attributes retrieved therein;

said data migration module being further configured for migrating data from the original host storage system to the replacement host storage system and for determining if data in the remote file migrated to the replacement host storage system is linked to one file or to more than one file in the original host storage system;

said data migration module being operative to create a file in the replacement host storage system and migrate the data from the original host storage system thereto if the data is only associated with one file;

said data migration module being further configured, in the event data in the remote file is linked to more than one file in the original host storage system, wherein said more than one file is two files, for determining if a file id and file system id are found in the data migration database in the replacement host storage system, if a file id and file system id are found in the data migration database, retrieving a replacement host storage system id for the more than one file and creating a hard link to the more than one file associated with the file system id retrieved, and if a file id and file system id are not found in the data migration database, for creating a file in the replacement host storage system, retrieving a file id for the newly created file in the replacement storage system file system from the original host storage system, migrating the data associated therewith to the replacement host storage system, and storing the retrieved file id for the file in the data migration database keyed by the file id and file system id retrieved from the file attributes from the original host storage system;

wherein said data migration module is further configured, in the event data in the remote file is linked to more than two files, for determining if a file id and file system id for each other file to which it is linked is found in the data migration database, for files whose file id and file system id are found in the data migration database, retrieving a replacement host storage system id for each other file and creating hard links to the file associated with the id identifier retrieved, and for each other file for which the file id and file system id are not found in the data migration database, for creating a new file in the replacement host storage system, retrieving a file id for each newly created file in the replacement host storage file system from the original host storage system, migrating the data associated therewith to the replacement host storage system from the original host storage system, and storing the retrieved file id for the file in the data migration database keyed by the file id and file system id retrieved from the file attributes, and creating a hard link to each other file in the data migration database; and

wherein said system is further configured for having all data in the original host storage system migrated to the replacement host storage system.

4. The system of claim 3 , wherein said data migration module is further configured for creating hard links between files whose file id and file system id are found in the data migration database and files in the replacement host storage system for which data is migrated from the original host system, for all files in the replacement host storage system associated with the same data.