diff --git a/benches/appendvec.rs b/benches/appendvec.rs
new file mode 100644
index 0000000000..cdfa31780a
--- /dev/null
+++ b/benches/appendvec.rs
@@ -0,0 +1,172 @@
+#![cfg_attr(feature = "unstable", feature(test))]
+extern crate rand;
+extern crate test;
+
+use rand::{thread_rng, Rng};
+use solana_runtime::appendvec::AppendVec;
+use std::path::Path;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, RwLock};
+use std::thread::spawn;
+use test::Bencher;
+
+const START_SIZE: u64 = 4 * 1024 * 1024;
+const INC_SIZE: u64 = 1 * 1024 * 1024;
+
+#[bench]
+fn appendvec_atomic_append(bencher: &mut Bencher) {
+    let path = Path::new("/media/nvme0/bench/bench_append");
+    let mut vec = AppendVec::<AtomicUsize>::new(path, true, START_SIZE, INC_SIZE);
+    bencher.iter(|| {
+        if vec.append(AtomicUsize::new(0)).is_none() {
+            assert!(vec.grow_file().is_ok());
+            assert!(vec.append(AtomicUsize::new(0)).is_some());
+        }
+    });
+    std::fs::remove_file(path).unwrap();
+}
+
+#[bench]
+fn appendvec_atomic_random_access(bencher: &mut Bencher) {
+    let path = Path::new("/media/nvme0/bench/bench_ra");
+    let mut vec = AppendVec::<AtomicUsize>::new(path, true, START_SIZE, INC_SIZE);
+    let size = 10_000_000;
+    for _ in 0..size {
+        if vec.append(AtomicUsize::new(0)).is_none() {
+            assert!(vec.grow_file().is_ok());
+            assert!(vec.append(AtomicUsize::new(0)).is_some());
+        }
+    }
+    bencher.iter(|| {
+        let index = thread_rng().gen_range(0, size as u64);
+        vec.get(index * std::mem::size_of::<AtomicUsize>() as u64);
+    });
+    std::fs::remove_file(path).unwrap();
+}
+
+#[bench]
+fn appendvec_atomic_random_change(bencher: &mut Bencher) {
+    let path = Path::new("/media/nvme0/bench/bench_rax");
+    let mut vec = AppendVec::<AtomicUsize>::new(path, true, START_SIZE, INC_SIZE);
+    let size = 10_000_000;
+    for _ in 0..size {
+        if vec.append(AtomicUsize::new(0)).is_none() {
+            assert!(vec.grow_file().is_ok());
+            assert!(vec.append(AtomicUsize::new(0)).is_some());
+        }
+    }
+    bencher.iter(|| {
+        let index = thread_rng().gen_range(0, size as u64);
+        let atomic1 = vec.get(index * std::mem::size_of::<AtomicUsize>() as u64);
+        let current1 = atomic1.load(Ordering::Relaxed);
+        let next = current1 + 1;
+        atomic1.store(next, Ordering::Relaxed);
+        let atomic2 = vec.get(index * std::mem::size_of::<AtomicUsize>() as u64);
+        let current2 = atomic2.load(Ordering::Relaxed);
+        assert_eq!(current2, next);
+    });
+    std::fs::remove_file(path).unwrap();
+}
+
+#[bench]
+fn appendvec_atomic_random_read(bencher: &mut Bencher) {
+    let path = Path::new("/media/nvme0/bench/bench_read");
+    let mut vec = AppendVec::<AtomicUsize>::new(path, true, START_SIZE, INC_SIZE);
+    let size = 100_000_000;
+    for _ in 0..size {
+        if vec.append(AtomicUsize::new(0)).is_none() {
+            assert!(vec.grow_file().is_ok());
+            assert!(vec.append(AtomicUsize::new(0)).is_some());
+        }
+    }
+    bencher.iter(|| {
+        let index = thread_rng().gen_range(0, size);
+        let atomic1 = vec.get((index * std::mem::size_of::<AtomicUsize>()) as u64);
+        let current1 = atomic1.load(Ordering::Relaxed);
+        assert_eq!(current1, 0);
+    });
+    std::fs::remove_file(path).unwrap();
+}
+
+#[bench]
+fn appendvec_concurrent_lock_append(bencher: &mut Bencher) {
+    let path = Path::new("bench_lock_append");
+    let vec = Arc::new(RwLock::new(AppendVec::<AtomicUsize>::new(
+        path, true, START_SIZE, INC_SIZE,
+    )));
+    let vec1 = vec.clone();
+    let size = 100_000_000;
+    let count = Arc::new(AtomicUsize::new(0));
+    let count1 = count.clone();
+    spawn(move || loop {
+        let mut len = count.load(Ordering::Relaxed);
+        {
+            let rlock = vec1.read().unwrap();
+            loop {
+                if rlock.append(AtomicUsize::new(0)).is_none() {
+                    break;
+                }
+                len = count.fetch_add(1, Ordering::Relaxed);
+            }
+            if len >= size {
+                break;
+            }
+        }
+        {
+            let mut wlock = vec1.write().unwrap();
+            if len >= size {
+                break;
+            }
+            assert!(wlock.grow_file().is_ok());
+        }
+    });
+    bencher.iter(|| {
+        let _rlock = vec.read().unwrap();
+        let len = count1.load(Ordering::Relaxed);
+        assert!(len < size * 2);
+    });
+    std::fs::remove_file(path).unwrap();
+}
+
+#[bench]
+fn appendvec_concurrent_get_append(bencher: &mut Bencher) {
+    let path = Path::new("bench_get_append");
+    let vec = Arc::new(RwLock::new(AppendVec::<AtomicUsize>::new(
+        path, true, START_SIZE, INC_SIZE,
+    )));
+    let vec1 = vec.clone();
+    let size = 100_000_000;
+    let count = Arc::new(AtomicUsize::new(0));
+    let count1 = count.clone();
+    spawn(move || loop {
+        let mut len = count.load(Ordering::Relaxed);
+        {
+            let rlock = vec1.read().unwrap();
+            loop {
+                if rlock.append(AtomicUsize::new(0)).is_none() {
+                    break;
+                }
+                len = count.fetch_add(1, Ordering::Relaxed);
+            }
+            if len >= size {
+                break;
+            }
+        }
+        {
+            let mut wlock = vec1.write().unwrap();
+            if len >= size {
+                break;
+            }
+            assert!(wlock.grow_file().is_ok());
+        }
+    });
+    bencher.iter(|| {
+        let rlock = vec.read().unwrap();
+        let len = count1.load(Ordering::Relaxed);
+        if len > 0 {
+            let index = thread_rng().gen_range(0, len);
+            rlock.get((index * std::mem::size_of::<AtomicUsize>()) as u64);
+        }
+    });
+    std::fs::remove_file(path).unwrap();
+}
diff --git a/runtime/Cargo.toml b/runtime/Cargo.toml
index d4d833a6c1..58727339ec 100644
--- a/runtime/Cargo.toml
+++ b/runtime/Cargo.toml
@@ -14,6 +14,7 @@ bv = { version = "0.11.0", features = ["serde"] }
 fnv = "1.0.6"
 hashbrown = "0.1.8"
 log = "0.4.2"
+memmap = "0.6.2"
 rand = "0.6.5"
 serde = "1.0.88"
 serde_derive = "1.0.88"
diff --git a/runtime/src/appendvec.rs b/runtime/src/appendvec.rs
new file mode 100644
index 0000000000..a763e4d414
--- /dev/null
+++ b/runtime/src/appendvec.rs
@@ -0,0 +1,336 @@
+use memmap::MmapMut;
+use solana_sdk::account::Account;
+use solana_sdk::pubkey::Pubkey;
+use std::fs::{File, OpenOptions};
+use std::io::{Error, ErrorKind, Result, Seek, SeekFrom, Write};
+use std::marker::PhantomData;
+use std::mem;
+use std::path::Path;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Mutex;
+
+const SIZEOF_U64: usize = mem::size_of::<u64>();
+
+pub struct AppendVec<T> {
+    data: File,
+    map: MmapMut,
+    current_offset: AtomicUsize,
+    append_lock: Mutex<()>,
+    file_size: u64,
+    inc_size: u64,
+    phantom: PhantomData<T>,
+}
+
+impl<T> AppendVec<T>
+where
+    T: Default,
+{
+    pub fn new(path: &Path, create: bool, size: u64, inc: u64) -> Self {
+        let mut data = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create(create)
+            .open(path)
+            .expect("Unable to open data file");
+
+        data.seek(SeekFrom::Start(size)).unwrap();
+        data.write_all(&[0]).unwrap();
+        data.seek(SeekFrom::Start(0)).unwrap();
+        data.flush().unwrap();
+        let map = unsafe { MmapMut::map_mut(&data).expect("failed to map the data file") };
+
+        AppendVec {
+            data,
+            map,
+            current_offset: AtomicUsize::new(0),
+            append_lock: Mutex::new(()),
+            file_size: size,
+            inc_size: inc,
+            phantom: PhantomData,
+        }
+    }
+
+    pub fn reset(&mut self) {
+        let _append_lock = self.append_lock.lock().unwrap();
+        self.current_offset.store(0, Ordering::Relaxed);
+    }
+
+    #[allow(dead_code)]
+    pub fn get(&self, index: u64) -> &T {
+        let offset = self.current_offset.load(Ordering::Relaxed);
+        let at = index as usize;
+        assert!(offset >= at + mem::size_of::<T>());
+        let data = &self.map[at..at + mem::size_of::<T>()];
+        let ptr = data.as_ptr() as *const T;
+        let x: Option<&T> = unsafe { ptr.as_ref() };
+        x.unwrap()
+    }
+
+    #[allow(dead_code)]
+    pub fn grow_file(&mut self) -> Result<()> {
+        if self.inc_size == 0 {
+            return Err(Error::new(ErrorKind::WriteZero, "Grow not supported"));
+        }
+        let _append_lock = self.append_lock.lock().unwrap();
+        let index = self.current_offset.load(Ordering::Relaxed) + mem::size_of::<T>();
+        if index as u64 + self.inc_size < self.file_size {
+            // grow was already called
+            return Ok(());
+        }
+        let end = self.file_size + self.inc_size;
+        drop(self.map.to_owned());
+        self.data.seek(SeekFrom::Start(end))?;
+        self.data.write_all(&[0])?;
+        self.data.seek(SeekFrom::Start(0))?;
+        self.data.flush()?;
+        self.map = unsafe { MmapMut::map_mut(&self.data)? };
+        self.file_size = end;
+        Ok(())
+    }
+
+    #[allow(dead_code)]
+    pub fn append(&self, val: T) -> Option<u64> {
+        let _append_lock = self.append_lock.lock().unwrap();
+        let index = self.current_offset.load(Ordering::Relaxed);
+
+        if (self.file_size as usize) < index + mem::size_of::<T>() {
+            return None;
+        }
+
+        let data = &self.map[index..(index + mem::size_of::<T>())];
+        unsafe {
+            let ptr = data.as_ptr() as *mut T;
+            std::ptr::write(ptr, val)
+        };
+        self.current_offset
+            .fetch_add(mem::size_of::<T>(), Ordering::Relaxed);
+        Some(index as u64)
+    }
+
+    fn get_account_size_static() -> usize {
+        mem::size_of::<u64>()
+            + mem::size_of::<Pubkey>()
+            + mem::size_of::<bool>()
+            + mem::size_of::<Pubkey>()
+    }
+
+    pub fn get_account(&self, index: u64) -> Result<Account> {
+        let mut at = index as usize;
+        let data = &self.map[at..(at + mem::size_of::<u64>())];
+        #[allow(clippy::cast_ptr_alignment)]
+        let size: u64 = unsafe { std::ptr::read_unaligned(data.as_ptr() as *const _) };
+        let len = size as usize;
+        at += SIZEOF_U64 as usize;
+
+        let offset = self.current_offset.load(Ordering::Relaxed);
+        assert!(offset >= at + len);
+
+        let data = &self.map[at..(at + mem::size_of::<u64>())];
+        #[allow(clippy::cast_ptr_alignment)]
+        let tokens: u64 = unsafe { std::ptr::read_unaligned(data.as_ptr() as *const _) };
+        at += mem::size_of::<u64>();
+
+        let userdata_len = len - Self::get_account_size_static();
+        let mut userdata = vec![];
+        userdata.extend_from_slice(&self.map[at..at + userdata_len]);
+        at += userdata_len;
+
+        let data = &self.map[at..(at + mem::size_of::<Pubkey>())];
+        let owner: Pubkey = unsafe { std::ptr::read(data.as_ptr() as *const _) };
+        at += mem::size_of::<Pubkey>();
+
+        let data = &self.map[at..(at + mem::size_of::<bool>())];
+        let executable: bool = unsafe { std::ptr::read(data.as_ptr() as *const _) };
+
+        Ok(Account {
+            tokens,
+            userdata,
+            owner,
+            executable,
+        })
+    }
+
+    pub fn append_account(&self, account: &Account) -> Option<u64> {
+        let _append_lock = self.append_lock.lock().unwrap();
+        let data_at = self.current_offset.load(Ordering::Relaxed);
+        let len = Self::get_account_size_static() + account.userdata.len();
+
+        if (self.file_size as usize) < data_at + len + SIZEOF_U64 {
+            return None;
+        }
+
+        let mut at = data_at as usize;
+        unsafe {
+            let data = &self.map[at..at + mem::size_of::<u64>()];
+            #[allow(clippy::cast_ptr_alignment)]
+            let ptr = data.as_ptr() as *mut u64;
+            std::ptr::write_unaligned(ptr, len as u64);
+            at += mem::size_of::<u64>();
+
+            let data = &self.map[at..at + mem::size_of::<u64>()];
+            #[allow(clippy::cast_ptr_alignment)]
+            let ptr = data.as_ptr() as *mut u64;
+            std::ptr::write_unaligned(ptr, account.tokens);
+            at += mem::size_of::<u64>();
+
+            let data = &self.map[at..at + account.userdata.len()];
+            let dst = data.as_ptr() as *mut u8;
+            let data = &account.userdata[0..account.userdata.len()];
+            let src = data.as_ptr();
+            std::ptr::copy_nonoverlapping(src, dst, account.userdata.len());
+            at += account.userdata.len();
+
+            let data = &self.map[at..at + mem::size_of::<Pubkey>()];
+            let ptr = data.as_ptr() as *mut Pubkey;
+            std::ptr::write(ptr, account.owner);
+            at += mem::size_of::<Pubkey>();
+
+            let data = &self.map[at..at + mem::size_of::<bool>()];
+            let ptr = data.as_ptr() as *mut bool;
+            std::ptr::write(ptr, account.executable);
+        };
+
+        self.current_offset
+            .fetch_add(len + SIZEOF_U64, Ordering::Relaxed);
+        Some(data_at as u64)
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+    use log::info;
+    use rand::{thread_rng, Rng};
+    use solana_sdk::timing::{duration_as_ms, duration_as_s};
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::time::Instant;
+
+    const START_SIZE: u64 = 4 * 1024 * 1024;
+    const INC_SIZE: u64 = 1 * 1024 * 1024;
+
+    #[test]
+    fn test_append_vec() {
+        let path = Path::new("append_vec");
+        let av = AppendVec::new(path, true, START_SIZE, INC_SIZE);
+        let val: u64 = 5;
+        let index = av.append(val).unwrap();
+        assert_eq!(*av.get(index), val);
+        let val1 = val + 1;
+        let index1 = av.append(val1).unwrap();
+        assert_eq!(*av.get(index), val);
+        assert_eq!(*av.get(index1), val1);
+        std::fs::remove_file(path).unwrap();
+    }
+
+    #[test]
+    fn test_append_vec_account() {
+        let path = Path::new("append_vec_account");
+        let av: AppendVec<Account> = AppendVec::new(path, true, START_SIZE, INC_SIZE);
+        let v1 = vec![1u8; 32];
+        let mut account1 = Account {
+            tokens: 1,
+            userdata: v1,
+            owner: Pubkey::default(),
+            executable: false,
+        };
+        let index1 = av.append_account(&account1).unwrap();
+        assert_eq!(index1, 0);
+        assert_eq!(av.get_account(index1).unwrap(), account1);
+
+        let v2 = vec![4u8; 32];
+        let mut account2 = Account {
+            tokens: 1,
+            userdata: v2,
+            owner: Pubkey::default(),
+            executable: false,
+        };
+        let index2 = av.append_account(&account2).unwrap();
+        let mut len = AppendVec::<Account>::get_account_size_static()
+            + account1.userdata.len()
+            + SIZEOF_U64 as usize;
+        assert_eq!(index2, len as u64);
+        assert_eq!(av.get_account(index2).unwrap(), account2);
+        assert_eq!(av.get_account(index1).unwrap(), account1);
+
+        account2.userdata.iter_mut().for_each(|e| *e *= 2);
+        let index3 = av.append_account(&account2).unwrap();
+        len += AppendVec::<Account>::get_account_size_static()
+            + account2.userdata.len()
+            + SIZEOF_U64 as usize;
+        assert_eq!(index3, len as u64);
+        assert_eq!(av.get_account(index3).unwrap(), account2);
+
+        account1.userdata.extend([1, 2, 3, 4, 5, 6].iter().cloned());
+        let index4 = av.append_account(&account1).unwrap();
+        len += AppendVec::<Account>::get_account_size_static()
+            + account2.userdata.len()
+            + SIZEOF_U64 as usize;
+        assert_eq!(index4, len as u64);
+        assert_eq!(av.get_account(index4).unwrap(), account1);
+        std::fs::remove_file(path).unwrap();
+    }
+
+    #[test]
+    fn test_grow_append_vec() {
+        let path = Path::new("grow");
+        let mut av = AppendVec::new(path, true, START_SIZE, INC_SIZE);
+        let mut val = [5u64; 32];
+        let size = 100_000;
+        let mut offsets = vec![0; size];
+
+        let now = Instant::now();
+        for index in 0..size {
+            if let Some(offset) = av.append(val) {
+                offsets[index] = offset;
+            } else {
+                assert!(av.grow_file().is_ok());
+                if let Some(offset) = av.append(val) {
+                    offsets[index] = offset;
+                } else {
+                    assert!(false);
+                }
+            }
+            val[0] += 1;
+        }
+        info!(
+            "time: {} ms {} / s",
+            duration_as_ms(&now.elapsed()),
+            ((mem::size_of::<[u64; 32]>() * size) as f32) / duration_as_s(&now.elapsed()),
+        );
+
+        let now = Instant::now();
+        let num_reads = 100_000;
+        for _ in 0..num_reads {
+            let index = thread_rng().gen_range(0, size);
+            assert_eq!(av.get(offsets[index])[0], (index + 5) as u64);
+        }
+        info!(
+            "time: {} ms {} / s",
+            duration_as_ms(&now.elapsed()),
+            (num_reads as f32) / duration_as_s(&now.elapsed()),
+        );
+        std::fs::remove_file(path).unwrap();
+    }
+
+    #[test]
+    fn random_atomic_change() {
+        let path = Path::new("random");
+        let mut vec = AppendVec::<AtomicUsize>::new(path, true, START_SIZE, INC_SIZE);
+        let size = 1_000;
+        for _ in 0..size {
+            if vec.append(AtomicUsize::new(0)).is_none() {
+                assert!(vec.grow_file().is_ok());
+                assert!(vec.append(AtomicUsize::new(0)).is_some());
+            }
+        }
+        let index = thread_rng().gen_range(0, size as u64);
+        let atomic1 = vec.get(index);
+        let current1 = atomic1.load(Ordering::Relaxed);
+        let next = current1 + 1;
+        atomic1.store(next, Ordering::Relaxed);
+        let atomic2 = vec.get(index);
+        let current2 = atomic2.load(Ordering::Relaxed);
+        assert_eq!(current2, next);
+        std::fs::remove_file(path).unwrap();
+    }
+}
diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
index a797fa286b..dbe11aef79 100644
--- a/runtime/src/lib.rs
+++ b/runtime/src/lib.rs
@@ -1,4 +1,5 @@
 mod accounts;
+pub mod appendvec;
 pub mod bank;
 pub mod bloom;
 mod last_id_queue;