Allocating files in a file system integrated with a RAID disk sub-system

• US 20070185942A1
• Filed: 03/13/2007
• Published: 08/09/2007
• Est. Priority Date: 06/03/1993
• Status: Active Grant

• Current Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Hitz, David, Rakitzis, Byron, Lau, James, Malcolm, Michael
• Granted Patent: US 7,818,498 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

Integrating a file system with a RAID array that exports precise information about the arrangement of data blocks in the RAID subsystem. The present invention uses separate current-write location (CWL) pointers for each disk in the disk array where the pointers simply advance through the disks as writes occur. The present invention writes on the disk with the lowest CWL pointer. A new disk is chosen only when the algorithm starts allocating space for a new file, or when it has allocated N blocks on the same disk for a single file. A sufficient number of blocks are defined as all the buffers in a chunk of N sequential buffers in a file. The result is that CWL pointers are never more than N blocks apart on different disks, and large files have N consecutive blocks on the same disk.

Claims

1. A method of storing data in a storage redundancy array that includes a plurality of storage devices, the method comprising:

for each of a plurality of blocks of data to be stored in the storage redundancy array,

selecting a block of data for which storage space has not yet been allocated;

determining whether said block of data is in a different file or in a different read ahead segment from a preceding block of data for which storage space in a first storage device of said plurality of storage devices in said array has been write allocated;

selecting storage space in a second storage device of said plurality of storage devices if said block of data is in a different file or is in a different read ahead segment from said preceding block, and

selecting storage space in said first storage device if said block of data is not in a different file or in a different read ahead segment from said preceding block.

2. The method of claim 1, further comprising:

for each of said plurality of blocks of data to be stored in the storage redundancy array,

assigning a write allocated storage block in said storage space to said block of data; and

adding said block of data to a list of writable blocks of data for said storage device.

3. The method of claim 2, further comprising:

writing unwritten blocks of data in said list of writable blocks of data to storage space allocated for said blocks of data in said storage redundancy array.

4. The method of claim 2, wherein said storage redundancy array is a RAID array.

5. A method of allocating data in a network storage system that includes a storage redundancy array, the method comprising:

identifying a set of metadata containers in the storage system which have dirty blocks, each said metadata container containing metadata for a separate data container of a plurality of data containers in the network storage system;

for each of the plurality of metadata containers in the storage system which has dirty blocks,

write allocating blocks of data referenced by said metadata container to a storage device in the storage redundancy array; and

adding said blocks of data to a list of writeable blocks of data for said storage device; and

flushing unwritten stripes of data to said storage redundancy array.

6. The method of claim 5, wherein at least two of the metadata containers correspond to separates file in the network storage system.

7. The method of claim 5, wherein said blocks of data are stored in a cache.

8. The method of claim 5, wherein said blocks of data referenced by each said metadata container are write allocated in a depth-first, post visit traversal of said blocks of data.

9. The method of claim 5, wherein said set of metadata containers comprises a first plurality of metadata containers corresponding to one or more directories and a second plurality of metadata containers corresponding to one or more files.

10. The method of claim 9, wherein each directory of said one or more directories is a specially formatted file.

11. The method of claim 9, wherein said first plurality of metadata containers are selected for write allocation before said second plurality of metadata containers.

12. The method of claim 11, wherein said second plurality of metadata containers are write allocated on a least recently used basis.

13. The method of claim 11, wherein said storage redundancy array is a RAID array.