Techniques for processing I/O requests

A method executed in a data storage system in connection with processing an I/O request, the method including:

• receiving the I/O request;
• determining whether the I/O request is a write request;
• and
• if the I/O request is a write request, performing write request processing including:
• copying write request data of the write request to cache;
• destaging the write request data from the cache to a primary storage device;
• and
• copying, in accordance with a heuristic, the write request data from the primary storage device to an asynchronous mirror device including an asynchronous copy of data from the primary storage device, wherein said asynchronous mirror device is write disabled with respect to received write requests requesting to write data thereto, said asynchronous mirror device used for servicing data requested in connection with read requests upon the occurrence of a cache miss, wherein said copying is performed using a background copy operation, and after destaging the write request data from cache to the primary storage device, a bit map is updated to indicate that a current copy of the write request data is stored in the primary storage device and not in the asynchronous mirror device, and after said copying copies the write request data to the asynchronous mirror device, the bit map is updated to indicates that the current copy of the write request data is stored in the primary storage device and the asynchronous mirror device, and wherein the bit map includes an entry for each partition of data of the primary storage device, and the background copy operation copies data to the asynchronous mirror device in chunks each having a size of a block, a size of said block being determined in accordance with internal processing performed on the asynchronous mirror device for garbage collection processing and wear leveling, said size being a multiple number of partitions of the primary storage device.

A data storage system comprising:

• a memory;
• a cache;
• a plurality of primary storage devices, said plurality of primary storage devices including disk devices;
• a plurality of asynchronous mirror devices, said plurality of asynchronous mirror devices including flash memory devices, wherein at least one of the plurality of primary storage devices is bound to one of said plurality of asynchronous mirror devices;
• bit map metadata stored in the memory and indicating that each of said at least one of the plurality of primary storage devices is bound to one of said plurality of asynchronous mirror devices;
• a bit map stored in the memory and associated with each binding represented in the bit map metadata, said each binding representing a binding of a first primary storage device to a first asynchronous mirror device, said bit map including bit map entries corresponding to portions of said first primary storage device, each of said bit map entries indicating whether a current copy of a corresponding portion of data of the first primary storage device is included in both the first primary storage device and the first asynchronous mirror device, or whether the current copy is included in the first primary storage device and not the first asynchronous mirror device;
• and
• a computer readable medium comprising executable code store thereon for processing a write request to write data to the first primary storage device, the executable code for processing a write request including code for:
• copying write request data of the write request to the cache;
• destaging the write request data to the first primary storage device;
• and
• copying, in accordance with a heuristic, the write request data from the first primary storage device to the first asynchronous mirror device including an asynchronous copy of data from the first primary storage device, wherein said first asynchronous mirror device is write disabled with respect to received write requests requesting to write data thereto, said first asynchronous mirror device used for servicing data requested in connection with read requests upon the occurrence of a cache miss, wherein said heuristic specifies a threshold amount of a block having a current copy which is stored on the first primary storage device and not on the first asynchronous mirror device and said copying copies a first block of the write request data from the first primary storage device to the first asynchronous mirror device when said threshold amount of the first block has a current copy stored on the first primary storage device and not on the first asynchronous mirror device.

A computer readable medium comprising executable code stored thereon for processing an I/O request in a data storage system, the computer readable medium comprising executable code for:

• receiving the I/O request;
• determining whether the I/O request is a write request;
• and
• if the I/O request is a write request, performing write request processing including:
• copying write request data of the write request to cache;
• destaging the write request data from the cache to a primary storage device;
• and
• copying, in accordance with a heuristic, the write request data from the primary storage device to an asynchronous mirror device including an asynchronous copy of data from the primary storage device, wherein said asynchronous mirror device is write disabled with respect to received write requests requesting to write data thereto, said asynchronous mirror device used for servicing data requested in connection with read requests upon the occurrence of a cache miss, wherein said heuristic specifies a threshold amount of a block having a current copy which is stored on the primary storage device and not on the asynchronous mirror device and said copying copies a first block of the write request data from the primary storage device to the asynchronous mirror device when said threshold amount of the first block has a current copy stored on the primary storage device and not on the asynchronous mirror device.

A data storage system comprising:

• a memory;
• a cache;
• a plurality of primary storage devices, said plurality of primary storage devices including disk devices;
• a plurality of asynchronous mirror devices, said plurality of asynchronous mirror devices including flash memory devices, wherein at least one of the plurality of primary storage devices is bound to one of said plurality of asynchronous mirror devices;
• bit map metadata stored in the memory and indicating that each of said at least one of the plurality of primary storage devices is bound to one of said plurality of asynchronous mirror devices;
• a bit map stored in the memory and associated with each binding represented in the bit map metadata, said each binding representing a binding of a first primary storage device to a first asynchronous mirror device, said bit map including bit map entries corresponding to portions of said first primary storage device, each of said bit map entries indicating whether a current copy of a corresponding portion of data of the first primary storage device is included in both the first primary storage device and the first asynchronous mirror device, or whether the current copy is included in the first primary storage device and not the first asynchronous mirror device;
• and
• a computer readable medium comprising executable code store thereon for processing a write request to write data to the first primary storage device, the executable code for processing a write request including code for:
• copying write request data of the write request to the cache;
• destaging the write request data to the first primary storage device;
• and
• copying, in accordance with a heuristic, the write request data from the first primary storage device to the first asynchronous mirror device including an asynchronous copy of data from the first primary storage device, wherein said first asynchronous mirror device is write disabled with respect to received write requests requesting to write data thereto, said first asynchronous mirror device used for servicing data requested in connection with read requests upon the occurrence of a cache miss, wherein said copying data from the first primary storage device to the first asynchronous mirror device copies data in blocks having a size determined in accordance with wear leveling and garbage collection processing performed internally on said first asynchronous mirror device.