Parallel block allocation for declustered logical disks

A computer program product for allocating space on a logical disk, the computer program product comprising:

• one or more computer readable tangible storage devices;
• program instructions stored on the one or more computer readable tangible storage devices, the program instructions comprising:
• program instructions to receive an allocation request to allocate a number of requested logical disk extents;
• program instructions to select one of a first group comprising an array of logical disk extents and a second group comprising an array of logical disk extents, the selected group having a number of free logical disk extents that is greater than or equal to the number of requested logical disk extents, the logical disk extents in the array of the first group and in the array of the second group corresponding to disk blocks on a logical disk, the logical disk spanning one or more physical random access disks;
• program instructions to lock the selected group to prevent allocating a logical disk extent other than in response to the allocation request;
• program instructions to, after the locking step, and prior to allocating the number of requested logical disk extents in the selected group, re-determine whether the selected group has a sufficient number of free logical disk extents to satisfy the received allocation request;
• program instructions to, responsive to re-determining that the selected group has a sufficient number of free logical disk extents, allocate the number of requested logical disk extents in the selected group, starting at a first index in the array of the selected group;
• program instructions to move a first pointer from the first index in the array of the selected group to a second index in the array of the selected group based at least in part on the number of requested logical disk extents;
• and
• program instructions to release the lock on the selected group to allow allocating a logical disk extent other than in response to the allocation request.

A computer system for allocating space on a logical disk, the computer system comprising:

• one or more computer processors;
• one or more computer readable tangible storage devices;
• and
• program instructions stored on at least one of the one or more computer readable tangible storage devices for execution by at least one of the one or more computer processors, the program instructions comprising:
• program instructions to receive an allocation request to allocate a number of requested logical disk extents;
• program instructions to select one of a first group comprising an array of logical disk extents and a second group comprising an array of logical disk extents, the selected group having a number of free logical disk extents that is greater than or equal to the number of requested logical disk extents, the logical disk extents in the array of the first group and in the array of the second group corresponding to disk blocks on a logical disk, the logical disk spanning one or more physical random access disks;
• program instructions to lock the selected group to prevent allocating a logical disk extent other than in response to the allocation request;
• program instructions to, after the locking step, and prior to allocating the number of requested logical disk extents in the selected group, re-determine whether the selected group has a sufficient number of free logical disk extents to satisfy the received allocation request;
• program instructions to, responsive to re-determining that the selected group has a sufficient number of free logical disk extents, allocate the number of requested logical disk extents in the selected group, starting at a first index in the array of the selected group;
• program instructions to move a first pointer from the first index in the array of the selected group to a second index in the array of the selected group based at least in part on the number of requested logical disk extents;
• and
• program instructions to release the lock on the selected group to allow allocating a logical disk extent other than in response to the allocation request.