Method and apparatus providing mass storage access from systems using different meta-data formats

• US 6,353,837 B1
• Filed: 06/30/1998
• Issued: 03/05/2002
• Est. Priority Date: 06/30/1998
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Blumenau, Steven M.
• Primary Examiner(s): Black, Thomas
• Assistant Examiner(s): RONES, CHARLES
• Application Number:
  US09/107,884
• Time in Patent Office: 1,344 Days
• Field of Search: 707/205, 707/102, 707/10, 709/250, 709/330, 710/68, 711/202, 360/48, 713/201, 713/100
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A method and apparatus for accessing storage from at least two different host computers features creating a first file having a first meta-data format and user data blocks in a mass storage medium using the first host computer and reading a logical to physical mapping of the user data blocks from the first file. A second file, having a second meta-data format, is created using a second host computer and the second file has blocks preallocated to be the same length as user data blocks of the first file. A logical to physical mapping of the preallocated user blocks is then obtained and the data blocks of the preallocated file are linked to the data blocks of the first file so that a reference to the preallocated blocks will provide an address at which the data requested can be read in the first file. In this manner, different meta-data blocks, corresponding to different filesystems, and/or operating systems, can be used in the respective first and second host computers.

Claims

1. A method for accessing data files of a mass storage device from at least two different host computers having different operating system meta-data formats, comprising the steps of:

creating, at first host computer, a first file having a first meta-data format and user blocks in said mass storage device,

determining at the first host computer a logical to physical mapping of the user data blocks from said first file,

creating at a second host computer a second file having a second meta-data format, said second file also having respective data blocks preallocated to be the same respective lengths as the user data blocks of the first file,

retrieving the logical to physical mapping of the preallocated blocks, and

linking the data blocks of the second file to the data blocks of the first file,

wherein the first file is comprised in a second file system associated with a second type of operating system, the first type of operating system is different from the second type of operating system, and if a call is made to the second file system to read one of the blocks of the second file, a reading of an associated on e of the blocks of the first file results.

2. The method of claim 1 further comprising the step of sending the logical to physical mapping of the first file to the second host computer over a communications channel.

3. The method of claim 1 wherein said linking step comprises the step of:

placing pointers in said preallocated data blocks of the second file which point to the user data blocks of said first file.

4. The method of claim 1 wherein said creation of the second file, no data from the user data blocks of the first file is sent to the second host computer.

5. A method for indirectly accessing data blocks comprising the steps of:

creating meta-data specifying a file,

setting an indirect storage flag in said meta-data,

writing in user data blocks an address identifying the corresponding indirectly stored data blocks, and

accessing said indirectly stored data blocks using the address data,

wherein the user data blocks and the meta-blocks and the meta-data file are comprised in a first file system associated with a first type of operating system residing in a first host computer, the indirectly stored data blocks are comprised in a second file system associated with a second type of operating system residing in a second host computer, the first type of operating system and the second type of operating system are different from each other, and the accessing of the indirectly stored data blocks is accomplished by making a call to the first file system to read the data file.

6. The method of claim 5 wherein said accessing step comprises the step of:

reading pointers in said data blocks containing user data of said data file, wherein any remainder of said user data blocks contain no user data.

7. A system for use in accessing data files of a mass storage device, the system comprising:

a first host computer that creates a first file having a first meta-data format and user data blocks in the mass storage device, the first host computer also determining a logical to physical mapping of the user data blocks from the first file,

a second host computer that creates a second file having a second meta-data format, the second file also having respective data blocks that are preallocated to be the same respective lengths as the user data blocks of the first file, the second host computer also retrieving the logical to physical mapping of the preallocated blocks, and

links between the data blocks of the second file and the data blocks of the first file,

wherein the first file is comprised in a first file system of a first type of operating system, the second file is comprised in a second file system of a second type of operating system, the first type of operating system and the system type of operating system are different from each other, and if a call is made to the second file system to read one of the blocks of the second file, a reading of an associated one of the blocks of the first file results.

8. The system of claim 7, further comprising a communications channel via which the logical to physical mapping of the first file may be sent to the second host computer.

9. The system of claim 7, wherein the preallocated data blocks comprise pointers that point to the user data blocks of the first file.

10. The system of claim 7, wherein during creation of the second file by the second host computer, no data from the user data blocks of the first file is sent to the second host computer.

11. A system for indirectly accessing data blocks, the system comprising:

a first host computer that creates meta-data specifying a data file, the meta-data including an indirect storage flag,

user data blocks comprising address data identifying corresponding indirectly stored data blocks, and

the first host computer accessing the indirectly stored data blocks using the address information,

wherein the meat-data and the user data blocks are comprised in a first file system associated with a first type of operating system residing in the first host computer, the indirectly stored data blocks are comprised in a second file system associated with a second type of operating system residing in a second host computer, the first type of operating system and the second type of operating system are different from each other, and the first host computer accesses the indirectly stored data blocks in response to a call to the first file system to read the data file.

12. The system of claim 11, wherein the user data blocks comprise pointers to other blocks containing user data file, and any remainder of the user data blocks contains no user data.