Method for writing contiguous arrays of stripes in a RAID storage system using mapped block writes

• US 7,930,475 B1
• Filed: 02/22/2007
• Issued: 04/19/2011
• Est. Priority Date: 03/21/2002
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Kleiman, Steven R., Sundaram, Rajesh, Doucette, Douglas P., Viswanathan, Srinivasan, Strange, Stephen H.
• Primary Examiner(s): NGUYEN, THAN VINH
• Application Number:
  US11/709,697
• Time in Patent Office: 1,517 Days
• Field of Search: None
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method for storing data on a plurality of storage devices of a storage system is disclosed. The data is received as data blocks from a plurality of write requests. The data blocks are saved as buffered data for writing to the storage devices in a single write request. An indication is received indicating the available storage blocks on the plurality of storage devices which are available for writing. The buffered data is associated with selected storage blocks of the storage blocks which are available for writing. The buffered data is written to the selected storage blocks in a single write request.

Claims

1. A method for storing data on a plurality of storage devices of a storage system, comprising:

receiving the data as data blocks from a plurality of write requests for one or more files;

saving the data blocks as buffered data for writing to the storage devices one file at a time;

selecting a next file to write allocate;

selecting a storage device with a lowest free disk block number (DBN) relative to a base offset;

allocating a next buffer of the selected file to the next lowest free DBN of the selected storage device;

checking if a full block layout has been write allocated;

repeating the allocating a next buffer step and the checking step until there are no more buffers for the selected file or a file block number (FBN) reaches a certain predetermined boundary;

determining that if the selected file has more buffers, proceeding to the selecting a storage device step; and

determining that if there are more files to write allocate, proceeding to the saving the data blocks step.

2. The method of claim 1, wherein the step of checking makes a determination of relative emptiness based on a file system layer maintaining a count of free blocks for each region of the storage devices, a count for each region forming a set of counts, and the set of counts can be searched to find a relatively empty region.

3. The method of claim 1, further comprising

prioritizing filling available space over providing maximal write chain lengths.

4. A storage system to store data on a plurality of storage devices, comprising:

a network adapter to receive the data as data blocks from a plurality of write requests for one or more files;

a memory to save the data blocks as buffered data for writing to the storage devices one file at a time;

a processor to select a next file to write allocate;

the processor to select a storage device with a lowest free disk block number (DBN) relative to a base offset;

the storage system to allocate a next buffer of the selected file to the next lowest free DBN of the selected storage device;

the processor to check if a full block layout has been write allocated;

the processor to repeat the allocate a next buffer, and the check until there are no more buffers for the selected file or a file block number (FBN) reaches is a certain predetermined boundary;

the processor to determine that if the selected file has more buffers, proceeding to select a storage device for the more buffers; and

the processor to determine that if there are more files to write allocate, proceeding to select a next file to write allocate.

5. The storage system of claim 4, further comprising:

the processor to make a determination of relative emptiness of different regions of the storage device,

where a file system maintains a count of free blocks for each region of the storage devices to form a set of counts, and the set of counts can be searched to find a relatively empty region.

6. The storage system of claim 4, further comprising:

the processor to prioritize filing available space over providing maximal write chain lengths.

7. A method for preparing a storage system to store data on a plurality of storage devices, comprising:

configuring the storage system to receive the data as data blocks from a plurality of write requests for one or more files;

configuring the storage system to save the data blocks as buffered data for writing to the storage devices one file at a time;

configuring the storage system to select a next file to write allocate;

.

configuring the storage system to select a storage device with a lowest free disk block number (DBN) relative to a base offset;

configuring the storage system to allocate a next buffer of the selected file to the next lowest free DBN of the selected storage device;

configuring the storage system to check if a full block layout has been write allocated;

configuring the storage system to repeat allocating a next buffer and is checking for the full block layout until there are no more buffers for the selected file or a file block number (FBN) reaches a certain predetermined boundary;

configuring the storage system to determine that if the selected file has more buffers, then proceeding to the step to select a storage device; and

configuring the storage system to determine that if there are more files to write allocate, then proceeding to the step to save the data blocks.

8. The method of claim 7, further comprising:

configuring the storage system to maintain a count of free blocks for each region of the storage devices to form a set of counts, and searching the set of counts to find a relatively empty region.

9. The method of claim 7, further comprising:

configuring the storage system to prioritize filling available space over providing maximal write chain lengths.

10. A computer readable storage media, comprising:

said computer readable storage media containing program instructions for execution on a processor for a method of storing data on a plurality of storage devices of a storage system, the program instructions for,

receiving the data as data blocks from a plurality of write requests for one or more files;

saving the data blocks as buffered data for writing to the storage devices one file at a time;

selecting a next file to write allocate;

selecting a storage device with a lowest free disk block number (DBN) relative to a base offset;

allocating a next buffer of the selected file to the next lowest free DBN of the selected storage device;

checking if a full block layout has been write allocated;

repeating the allocating a next buffer instruction and the checking instruction until there are no more buffers for the selected file or a file block number (FBN) reaches a certain predetermined boundary;

determining that if the selected file has more buffers, proceeding to the selecting a storage device instruction; and

determining that if there are more files to write allocate, proceeding to the saving the data blocks instruction.