Mehthod and apparatus for supporting snapshots with direct I/O in a storage area network

A file server for a storage area network having a file system that utilizes an access protocol for file system access, said file server configured to:

• start to maintain, at a time T1, a time T1 snapshot volume of a live volume of data in the file system;
• receive, from a client C1 at a time subsequent to T1, an update access request for a portion of a file that includes data stored in access unit B1 of the live volume;
• and
• responsive to the update access request, allocate, to the time T1 snapshot volume, a new access unit B2 corresponding to access unit B1, and copy data stored in access unit B1 to access unit B2.

A network comprising a file server, a client C1, and a storage system having a live volume of a file system stored thereon and using an access protocol for file system access, wherein said file server is configured to:

• start to maintain, at a time T1, a time T1 snapshot volume of the live volume of data in the file system;
• receive, from said client C1 at a time subsequent to T1, an update access request for a portion of a file that includes data stored in access unit B1 of the live volume;
• and
• responsive to the update access request, allocate, to the time T1 snapshot volume, a new access unit B2 corresponding to access unit B1, and copy data stored in access unit B1 to access unit B2;
• and said client C1 is configured to:
• transmit the first update request for a portion of a file including data stored in access unit B1 of the live volume to the file server.

A machine readable medium or media having recorded thereon instructions configured to instruct a process of a file server in a storage area network having a file system that utilizes an access protocol for file system access to:

• start to maintain, at a time T1, a time T1 snapshot volume of a live volume of data in the file system;
• receive, from a client C1 at a time subsequent to T1, an update access request for a portion of a file that includes data stored in access unit B1 of the live volume;
• and
• responsive to the update access request, allocate, to the time T1 snapshot volume, a new access unit B2 corresponding to access unit B1, and copy data stored in access unit B1 to access unit B2.