diff --git a/rabin/global/config.c b/rabin/global/config.c
index bbba2a1..822707a 100644
--- a/rabin/global/config.c
+++ b/rabin/global/config.c
@@ -176,7 +176,7 @@ read_config(char *configfile, archive_config_t *cfg)
 	cfg->verify_chunks = 0;
 	cfg->algo = COMPRESS_LZ4;
 	cfg->chunk_cksum_type = DEFAULT_CKSUM;
-	cfg->similarity_interval = DEFAULT_SIMILARITY_INTERVAL;
+	cfg->pct_interval = DEFAULT_SIMILARITY_INTERVAL;
 
 	fh = fopen(configfile, "r");
 	if (fh == NULL) {
@@ -286,6 +286,7 @@ read_config(char *configfile, archive_config_t *cfg)
 		cfg->directory_levels = 3;
 	}
 
+	cfg->segment_sz_bytes = segment_sz_bytes;
 	cfg->segment_sz = segment_sz_bytes / cfg->chunk_sz_bytes;
 
 	total_dirs = 1;
@@ -329,8 +330,8 @@ write_config(char *configfile, archive_config_t *cfg)
 }
 
 int
-set_simple_config(archive_config_t *cfg, compress_algo_t algo, cksum_t ck, uint32_t chunksize,
-		  size_t file_sz, uint32_t chunks_per_seg)
+set_config_s(archive_config_t *cfg, compress_algo_t algo, cksum_t ck, uint32_t chunksize,
+		  size_t file_sz, int pct_interval)
 {
 	cfg->algo = algo;
 	cfg->chunk_cksum_type = ck;
@@ -338,6 +339,7 @@ set_simple_config(archive_config_t *cfg, compress_algo_t algo, cksum_t ck, uint3
 	cfg->chunk_cksum_sz = get_cksum_sz(cfg->chunk_cksum_type);
 	cfg->chunk_sz = chunksize;
 	cfg->chunk_sz_bytes = RAB_BLK_AVG_SZ(cfg->chunk_sz);
+	cfg->pct_interval = pct_interval;
 
 	cfg->archive_sz = file_sz;
 	if (cfg->archive_sz < ONE_TB) {
@@ -346,5 +348,10 @@ set_simple_config(archive_config_t *cfg, compress_algo_t algo, cksum_t ck, uint3
 	} else {
 		segment_sz_bytes = EIGHT_MB;
 	}
+
+	cfg->segment_sz_bytes = segment_sz_bytes;
+	cfg->segment_sz = segment_sz_bytes / cfg->chunk_sz_bytes;
+
+	return (0);
 }
 
diff --git a/rabin/global/config.h b/rabin/global/config.h
index 91199be..58574f8 100644
--- a/rabin/global/config.h
+++ b/rabin/global/config.h
@@ -46,22 +46,24 @@ typedef struct {
 	compress_algo_t compress_level; // Default preset compression level per algo.
 	cksum_t chunk_cksum_type; // Which digest to use for hash based chunk lookup.
 	int chunk_cksum_sz; // Size of cksum in bytes.
-	int similarity_interval; // Similarity based match intervals in %age.
+	int pct_interval; // Similarity based match intervals in %age.
 			// The items below are computed given the above
 			// components.
 
 	uint32_t chunk_sz_bytes; // Average chunk size
-	uint32_t segment_sz; // Number of chunks
+	uint32_t segment_sz_bytes; // Segment size in bytes
+	uint32_t segment_sz; // Number of chunks in one segment
 	uint32_t container_sz; // Number of segments
 	int directory_fanout; // Number of subdirectories in a directory
 	int directory_levels; // Levels of nested directories
 	int num_containers; // Number of containers in a directory
+	void *dbdata;
 } archive_config_t;
 
 int read_config(char *configfile, archive_config_t *cfg);
 int write_config(char *configfile, archive_config_t *cfg);
-int set_simple_config(archive_config_t *cfg, compress_algo_t algo, cksum_t ck,
-		      uint32_t chunksize, size_t file_sz, uint32_t chunks_per_seg);
+int set_config_s(archive_config_t *cfg, compress_algo_t algo, cksum_t ck,
+		      uint32_t chunksize, size_t file_sz, int pct_interval);
 
 #ifdef	__cplusplus
 }
diff --git a/rabin/global/initdb.c b/rabin/global/initdb.c
index 96fdcee..2fd548b 100644
--- a/rabin/global/initdb.c
+++ b/rabin/global/initdb.c
@@ -28,7 +28,8 @@
 #include <stdio.h>
 #include <errno.h>
 #include <utils.h>
-#include <config.h>
+#include <allocator.h>
+#include <pthread.h>
 
 #include "initdb.h"
 #include "config.h"
@@ -38,6 +39,28 @@
 #define	FOUR_MB (4194304ULL)
 #define	EIGHT_MB (8388608ULL)
 
+/*
+ * Hashtable structures for in-memory index.
+ */
+typedef struct _hash_entry {
+	uchar_t *cksum;
+	struct _hash_entry *next;
+	struct _hash_entry *lru_prev;
+	struct _hash_entry *lru_next;
+} hash_entry_t;
+
+typedef struct {
+	hash_entry_t **htab;
+} htab_t;
+
+typedef struct {
+	htab_t *htablst;
+	pthread_mutex_t *mlist;
+	hash_entry_t *lru_head;
+	hash_entry_t *lru_tail;
+	uint64_t memlimit;
+	uint64_t memused;
+} htablst_t;
 
 archive_config_t *
 init_global_db(char *configfile)
@@ -59,12 +82,67 @@ init_global_db(char *configfile)
 }
 
 archive_config_t *
-init_global_db_simple(char *path, uint32_t chunksize, uint32_t chunks_per_seg,
+init_global_db_s(char *path, uint32_t chunksize, int pct_interval,
 		      compress_algo_t algo, cksum_t ck, size_t file_sz, size_t memlimit)
 {
 	archive_config_t *cfg;
 	int rv;
+	float diff;
 
 	cfg = calloc(1, sizeof (archive_config_t));
-	rv = set_simple_config(cfg, algo, ck, chunksize, file_sz, chunks_per_seg);
+	rv = set_config_s(cfg, algo, ck, chunksize, file_sz, chunks_per_seg, pct_interval);
+
+	if (path != NULL) {
+		printf("Disk based index not yet implemented.\n");
+		free(cfg);
+		return (NULL);
+	} else {
+		uint32_t hash_slots, intervals, i;
+		uint64_t memreqd;
+		htablst_t *htablst;
+
+		// Compute total hashtable entries first
+		intervals = 100 / pct_interval - 1;
+		hash_slots = file_sz / cfg->segment_sz_bytes + 1;
+		hash_slots *= intervals;
+
+		// Compute memory required to hold all hash entries assuming worst case 50%
+		// occupancy.
+		memreqd = hash_slots * (sizeof (hash_entry_t) + cfg->chunk_cksum_sz +
+			sizeof (hash_entry_t *) + (sizeof (hash_entry_t *)) / 2);
+		memreqd += hash_slots * sizeof (hash_entry_t **);
+		diff = (float)pct_interval / 100.0;
+
+		// Reduce hash_slots to remain within memlimit
+		while (memreqd > memlimit) {
+			hash_slots -= (hash_slots * diff);
+			memreqd = hash_slots * (sizeof (hash_entry_t) +
+					cfg->chunk_cksum_sz + sizeof (hash_entry_t *) + 
+					(sizeof (hash_entry_t *)) / 2);
+			memreqd += hash_slots * sizeof (hash_entry_t **);
+		}
+
+		// Now create as many hash tables as there are similarity match intervals
+		// each having hash_slots / intervals slots.
+		htablst = calloc(1, sizeof (htablst_t));
+		htablst->memlimit = memlimit;
+		htablst->htablst = (htab_t *)calloc(intervals, sizeof (htab_t));
+		htablst->mlist = (pthread_mutex_t *)malloc(intervals * sizeof (pthread_mutex_t));
+
+		for (i = 0; i < intervals; i++) {
+			htablst->htablst[i].htab = (hash_entry_t **)calloc(hash_slots / intervals,
+							sizeof (hash_entry_t *));
+			htablst->memused += ((hash_slots / intervals) * (sizeof (hash_entry_t *)));
+			pthread_mutex_init(&(htablst->mlist[i]), NULL);
+		}
+		cfg->dbdata = htablst;
+		slab_cache_add(sizeof (hash_entry_t));
+		slab_cache_add(cfg->chunk_cksum_sz);
+	}
+	return (cfg);
+}
+
+int
+db_insert_s(archive_config_t *cfg, uchar_t *cksum, int interval_num)
+{
 }
diff --git a/rabin/global/initdb.h b/rabin/global/initdb.h
index 803fd06..f51b968 100644
--- a/rabin/global/initdb.h
+++ b/rabin/global/initdb.h
@@ -26,8 +26,8 @@ extern "C" {
 #endif
 
 archive_config_t *init_global_db(char *configfile);
-archive_config_t *init_global_db_simple(char *path, uint32_t chunksize, uint32_t chunks_per_seg,
-		      compress_algo_t algo, cksum_t ck, size_t file_sz, size_t memlimit)
+archive_config_t *init_global_db_s(char *path, uint32_t chunksize, int pct_interval,
+			compress_algo_t algo, cksum_t ck, size_t file_sz, size_t memlimit);
 
 #ifdef	__cplusplus
 }
diff --git a/rabin/rabin_dedup.h b/rabin/rabin_dedup.h
index 1feae91..d4d3424 100644
--- a/rabin/rabin_dedup.h
+++ b/rabin/rabin_dedup.h
@@ -149,6 +149,11 @@ typedef struct rab_blockentry {
 	struct rab_blockentry *next;
 } rabin_blockentry_t;
 
+typedef struct global_blockentry {
+	uint64_t offset;
+	uint32_t length;
+} global_blockentry_t;
+
 typedef struct {
 	unsigned char *current_window_data;
 	rabin_blockentry_t **blocks;