diff --git a/runtime/src/accounts.rs b/runtime/src/accounts.rs
index 5834bb3f5d..4cacae406b 100644
--- a/runtime/src/accounts.rs
+++ b/runtime/src/accounts.rs
@@ -8,6 +8,7 @@ use crate::blockhash_queue::BlockhashQueue;
 use crate::message_processor::has_duplicates;
 use bincode::serialize;
 use log::*;
+use rayon::slice::ParallelSliceMut;
 use solana_metrics::inc_new_counter_error;
 use solana_sdk::account::Account;
 use solana_sdk::hash::{Hash, Hasher};
@@ -100,12 +101,16 @@ impl Accounts {
     }
 
     pub fn new(in_paths: Option<String>) -> Self {
+        Self::new_with_num_stores(in_paths, 0)
+    }
+
+    pub fn new_with_num_stores(in_paths: Option<String>, min_num_stores: usize) -> Self {
         let (paths, own_paths) = if in_paths.is_none() {
             (Self::make_default_paths(), true)
         } else {
             (in_paths.unwrap(), false)
         };
-        let accounts_db = Arc::new(AccountsDB::new(&paths));
+        let accounts_db = Arc::new(AccountsDB::new_with_num_stores(&paths, min_num_stores));
         Accounts {
             accounts_db,
             account_locks: Mutex::new(HashSet::new()),
@@ -332,7 +337,9 @@ impl Accounts {
         );
 
         let mut versions: Vec<(Pubkey, u64, B)> = accumulator.into_iter().flat_map(|x| x).collect();
-        versions.sort_by_key(|s| (s.0, s.1));
+        self.accounts_db.thread_pool.install(|| {
+            versions.par_sort_by_key(|s| (s.0, s.1));
+        });
         versions.dedup_by_key(|s| s.0);
         versions
             .into_iter()
diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index a3624418c8..de046707bb 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -40,7 +40,7 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, RwLock};
 use sys_info;
 
-const ACCOUNT_DATA_FILE_SIZE: u64 = 16 * 1024 * 1024;
+const ACCOUNT_DATA_FILE_SIZE: u64 = 4 * 1024 * 1024;
 const ACCOUNT_DATA_FILE: &str = "data";
 pub const NUM_THREADS: u32 = 10;
 
@@ -78,8 +78,11 @@ pub type InstructionAccounts = Vec<Account>;
 pub type InstructionCredits = Vec<LamportCredit>;
 pub type InstructionLoaders = Vec<Vec<(Pubkey, Account)>>;
 
+// Each fork has a set of storage entries.
+type ForkStores = HashMap<usize, Arc<AccountStorageEntry>>;
+
 #[derive(Default, Debug)]
-pub struct AccountStorage(HashMap<Fork, HashMap<usize, Arc<AccountStorageEntry>>>);
+pub struct AccountStorage(HashMap<Fork, ForkStores>);
 
 struct AccountStorageVisitor;
 
@@ -275,7 +278,9 @@ pub struct AccountsDB {
     file_size: u64,
 
     /// Thread pool used for par_iter
-    thread_pool: ThreadPool,
+    pub thread_pool: ThreadPool,
+
+    min_num_stores: usize,
 }
 
 pub fn get_paths_vec(paths: &str) -> Vec<String> {
@@ -295,11 +300,18 @@ impl Default for AccountsDB {
                 .num_threads(2)
                 .build()
                 .unwrap(),
+            min_num_stores: 0,
         }
     }
 }
 
 impl AccountsDB {
+    pub fn new_with_num_stores(paths: &str, min_num_stores: usize) -> Self {
+        let mut new = Self::new(paths);
+        new.min_num_stores = min_num_stores;
+        new
+    }
+
     pub fn new_with_file_size(paths: &str, file_size: u64) -> Self {
         let paths = get_paths_vec(&paths);
         AccountsDB {
@@ -313,6 +325,7 @@ impl AccountsDB {
                 .num_threads(sys_info::cpu_num().unwrap_or(NUM_THREADS) as usize)
                 .build()
                 .unwrap(),
+            min_num_stores: 0,
         }
     }
 
@@ -359,12 +372,12 @@ impl AccountsDB {
         Ok(())
     }
 
-    fn new_storage_entry(&self, fork_id: Fork, path: &str) -> AccountStorageEntry {
+    fn new_storage_entry(&self, fork_id: Fork, path: &str, size: u64) -> AccountStorageEntry {
         AccountStorageEntry::new(
             path,
             fork_id,
             self.next_id.fetch_add(1, Ordering::Relaxed),
-            self.file_size,
+            size,
         )
     }
 
@@ -491,11 +504,31 @@ impl AccountsDB {
         }
         drop(stores);
 
-        let mut stores = self.storage.write().unwrap();
-        let path_index = thread_rng().gen_range(0, self.paths.len());
-        let fork_storage = stores.0.entry(fork_id).or_insert_with(HashMap::new);
-        let store = Arc::new(self.new_storage_entry(fork_id, &self.paths[path_index]));
+        let store = self.create_and_insert_store(fork_id, self.file_size);
         store.try_available();
+        store
+    }
+
+    fn create_and_insert_store(&self, fork_id: Fork, size: u64) -> Arc<AccountStorageEntry> {
+        let mut stores = self.storage.write().unwrap();
+        let fork_storage = stores.0.entry(fork_id).or_insert_with(HashMap::new);
+
+        // Create more stores so that when scanning the storage all CPUs have work
+        while fork_storage.len() < self.min_num_stores {
+            self.create_store(fork_id, fork_storage, self.file_size);
+        }
+
+        self.create_store(fork_id, fork_storage, size)
+    }
+
+    fn create_store(
+        &self,
+        fork_id: Fork,
+        fork_storage: &mut ForkStores,
+        size: u64,
+    ) -> Arc<AccountStorageEntry> {
+        let path_index = thread_rng().gen_range(0, self.paths.len());
+        let store = Arc::new(self.new_storage_entry(fork_id, &self.paths[path_index], size));
         fork_storage.insert(store.id, store.clone());
         store
     }
@@ -537,6 +570,12 @@ impl AccountsDB {
             let rvs = storage.accounts.append_accounts(&with_meta[infos.len()..]);
             if rvs.is_empty() {
                 storage.set_status(AccountStorageStatus::Full);
+
+                // See if an account overflows the default append vec size.
+                let data_len = (with_meta[infos.len()].1.data.len() + 4096) as u64;
+                if data_len > self.file_size {
+                    self.create_and_insert_store(fork_id, data_len * 2);
+                }
                 continue;
             }
             for (offset, (_, account)) in rvs.iter().zip(&with_meta[infos.len()..]) {
@@ -1374,4 +1413,21 @@ mod tests {
             });
         assert_eq!(accounts.len(), 2);
     }
+
+    #[test]
+    fn test_store_large_account() {
+        solana_logger::setup();
+        let paths = get_tmp_accounts_path!();
+        let db = AccountsDB::new(&paths.paths);
+
+        let key = Pubkey::default();
+        let data_len = ACCOUNT_DATA_FILE_SIZE as usize + 7;
+        let account = Account::new(1, data_len, &key);
+
+        db.store(0, &hashmap!(&key => &account));
+
+        let ancestors = vec![(0, 0)].into_iter().collect();
+        let ret = db.load_slow(&ancestors, &key).unwrap();
+        assert_eq!(ret.0.data.len(), data_len);
+    }
 }
diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index d7a3cc51b0..c66f902f19 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -50,6 +50,12 @@ use std::sync::{Arc, RwLock, RwLockReadGuard};
 
 pub const SECONDS_PER_YEAR: f64 = (365.0 * 24.0 * 60.0 * 60.0);
 
+// Create many append vecs to increase parallelism in scan_ functions.
+fn default_num_stores() -> usize {
+    const DEFAULT_NUM_STORES: u32 = 8;
+    sys_info::cpu_num().unwrap_or(DEFAULT_NUM_STORES) as usize
+}
+
 type BankStatusCache = StatusCache<Result<()>>;
 
 #[derive(Default)]
@@ -63,7 +69,7 @@ pub struct BankRc {
 
 impl BankRc {
     pub fn new(account_paths: Option<String>, id: AppendVecId) -> Self {
-        let accounts = Accounts::new(account_paths);
+        let accounts = Accounts::new_with_num_stores(account_paths, default_num_stores());
         accounts
             .accounts_db
             .next_id
@@ -280,7 +286,7 @@ impl Bank {
     pub fn new_with_paths(genesis_block: &GenesisBlock, paths: Option<String>) -> Self {
         let mut bank = Self::default();
         bank.ancestors.insert(bank.slot(), 0);
-        bank.rc.accounts = Arc::new(Accounts::new(paths));
+        bank.rc.accounts = Arc::new(Accounts::new_with_num_stores(paths, default_num_stores()));
         bank.process_genesis_block(genesis_block);
         // genesis needs stakes for all epochs up to the epoch implied by
         //  slot = 0 and genesis configuration