Restore of secondary data using thread pooling

A system for restoring data from secondary storage to primary storage, the system comprising:

• a secondary storage controller computer comprising computer hardware and in communication with one or more secondary storage devices in a secondary storage subsystem, the secondary storage controller computer configured to:
• maintain a look-ahead thread pool having a number of look-ahead restore threads executing on one or more processors of the secondary storage controller computer;
• receive a restore request to restore a secondary copy of primary data from the one or more secondary storage devices in the secondary storage subsystem to one or more primary storage devices in a primary storage subsystem;
• select at least a first look-ahead restore thread in the look-ahead thread pool to use to process the restore request;
• retrieve the secondary copy from the one or more secondary storage devices, by causing the first look-ahead thread in the look-ahead thread pool to (i) process a data structure that includes a number of data blocks arranged in a first order within the secondary copy, and (ii) generate a second order for reading the number of data blocks that is different from the first order;
• read the number of data blocks from the one or more secondary storage devices according to the second order;
• forward the retrieved secondary copy to the primary storage subsystem for storage on the one or more primary storage devices;
• and
• adjust, based on one or more performance metrics associated with the first look-ahead restore thread of the look-ahead thread pool, the number of look-ahead restore threads in the look-ahead thread pool.