Divide the extent read into a vector or parallel disk reads.

fdbserver/Knobs.cpp

@@ -704,7 +704,8 @@ void ServerKnobs::initialize(bool randomize, ClientKnobs* clientKnobs, bool isSi
 	init( FASTRESTORE_RATE_UPDATE_SECONDS,                       1.0 ); if( randomize && BUGGIFY ) { FASTRESTORE_RATE_UPDATE_SECONDS = deterministicRandom()->random01() < 0.5 ? 0.1 : 2;}
 
 	init( REDWOOD_DEFAULT_PAGE_SIZE,                            4096 );
-	init( REDWOOD_DEFAULT_EXTENT_SIZE,                       1048576 );
+	init( REDWOOD_DEFAULT_EXTENT_SIZE,              32 * 1024 * 1024 );
+	init( REDWOOD_DEFAULT_EXTENT_READ_SIZE,              1024 * 1024 );
 	init( REDWOOD_KVSTORE_CONCURRENT_READS,                       64 );
 	init( REDWOOD_COMMIT_CONCURRENT_READS,                        64 );
 	init( REDWOOD_EXTENT_CONCURRENT_READS,                         4 );

fdbserver/Knobs.h

@@ -638,6 +638,7 @@ public:
 
 	int REDWOOD_DEFAULT_PAGE_SIZE; // Page size for new Redwood files
 	int REDWOOD_DEFAULT_EXTENT_SIZE; // Extent size for new Redwood files
+	int REDWOOD_DEFAULT_EXTENT_READ_SIZE; // Extent read size for Redwood files
 	int REDWOOD_KVSTORE_CONCURRENT_READS; // Max number of simultaneous point or range reads in progress.
 	int REDWOOD_COMMIT_CONCURRENT_READS; // Max number of concurrent reads done to support commit operations
 	int REDWOOD_EXTENT_CONCURRENT_READS; // Max number of simultaneous extent disk reads in progress.