diff --git a/CMakeLists.txt b/CMakeLists.txt
index 568045d5d..667b0bdb0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,6 +25,7 @@ set(storagemanager_SRCS
     src/S3Storage.cpp
     src/LocalStorage.cpp
     src/Cache.cpp
+    src/Downloader.cpp
 )
 
 option(TRACE "Enable some tracing output" OFF)
diff --git a/src/Cache.cpp b/src/Cache.cpp
index 914d79576..d3e27e786 100644
--- a/src/Cache.cpp
+++ b/src/Cache.cpp
@@ -1,9 +1,11 @@
 
 #include "Cache.h"
 #include "Config.h"
+#include "Downloader.h"
 #include <iostream>
 #include <syslog.h>
 #include <boost/filesystem.hpp>
+#include <boost/thread.hpp>
 
 using namespace std;
 using namespace boost::filesystem;
@@ -49,6 +51,7 @@ Cache::Cache()
     }
     cout << "Cache got prefix " << prefix << endl;
     
+    downloader.setDownloadPath(prefix.string());
 }
 
 Cache::~Cache()
@@ -57,8 +60,81 @@ Cache::~Cache()
 
 void Cache::read(const vector<string> &keys)
 {
+/*
+    move existing keys to a do-not-evict map
+    fetch keys that do not exist
+    after fetching, move all keys from do-not-evict to the back of the LRU
+*/
+    boost::unique_lock<boost::mutex> s(lru_mutex);
+    vector<const string *> keysToFetch;
+    
+    uint i;
+    M_LRU_t::iterator mit;
+    
+    for (const string &key : keys)
+    {
+        mit = m_lru.find(key);
+        if (mit != m_lru.end())
+            // it's in the cache, add the entry to the do-not-evict set
+            addToDNE(mit->lit);
+        else
+            // not in the cache, put it in the list to download
+            keysToFetch.push_back(&key);
+    }
+    s.unlock();
+    
+    // start downloading the keys to fetch
+    if (!keysToFetch.empty())
+        downloader.download(keysToFetch);
+    
+    s.lock();
+    
+    // move all keys to the back of the LRU
+    for (const string &key : keys)
+    {
+        mit = m_lru.find(key);
+        if (mit != m_lru.end())
+            lru.splice(lru.end(), lru, mit->lit);
+        else
+        {
+            lru.push_back(key);
+            m_lru.insert(M_LRU_element_t(&(lru.back()), lru.end()--));
+        }
+        removeFromDNE(lru.end());
+    }
 }
 
+Cache::DNEElement::DNEElement(const LRU_t::iterator &k) : key(k), refCount(1)
+{
+}
+        
+void Cache::addToDNE(const LRU_t::iterator &key)
+{
+    DNEElement e(key);
+    DNE_t::iterator it = doNotEvict.find(e);
+    if (it != doNotEvict.end())
+    {
+        DNEElement &dnee = const_cast<DNEElement &>(*it);
+        ++dnee.refCount;
+    }
+    else
+        doNotEvict.insert(e);
+}
+        
+void Cache::removeFromDNE(const LRU_t::iterator &key)
+{
+    DNEElement e(key);
+    DNE_t::iterator it = doNotEvict.find(e);
+    if (it == doNotEvict.end())
+        return;
+    DNEElement &dnee = const_cast<DNEElement &>(*it);
+    if (--dnee.refCount == 0)
+        doNotEvict.erase(it);
+}
+    
+        
+
+        
 void Cache::exists(const vector<string> &keys, vector<bool> *out)
 {
 }
@@ -79,4 +155,40 @@ void Cache::makeSpace(size_t size)
 {
 }
 
+
+/* The helper classes */
+
+Cache::M_LRU_element_t::M_LRU_element_t(const string *k) : key(k)
+{}
+
+Cache::M_LRU_element_t::M_LRU_element_t(const string &k) : key(&k)
+{}
+
+Cache::M_LRU_element_t::M_LRU_element_t(const string *k, const LRU_t::iterator &i) : key(k), lit(i)
+{}
+
+inline size_t Cache::KeyHasher::operator()(const M_LRU_element_t &l) const
+{
+    return hash<string>()(*(l.key));
 }
+
+inline bool Cache::KeyEquals::operator()(const M_LRU_element_t &l1, const M_LRU_element_t &l2) const
+{
+    return (*(l1.key) == *(l2.key));
+}
+
+inline size_t Cache::DNEHasher::operator()(const DNEElement &l) const
+{
+    return hash<string>()(*(l.key));
+}
+
+inline bool Cache::DNEEquals::operator()(const DNEElement &l1, const DNEElement &l2) const
+{
+    return (*(l1.key) == *(l2.key));
+}
+
+}
+
+
+
+
diff --git a/src/Cache.h b/src/Cache.h
index a32cac474..11df01d71 100644
--- a/src/Cache.h
+++ b/src/Cache.h
@@ -2,10 +2,15 @@
 #ifndef CACHE_H_
 #define CACHE_H_
 
+#include "Downloader.h"
+
 #include <string>
 #include <vector>
+#include <list>
+#include <unordered_set>
 #include <boost/utility.hpp>
 #include <boost/filesystem/path.hpp>
+#include <boost/thread/mutex.hpp>
 
 namespace storagemanager
 {
@@ -26,9 +31,62 @@ class Cache : public boost::noncopyable
     private:
         boost::filesystem::path prefix;
         size_t maxCacheSize;
+
+        /* The main cache structures */
+        typedef std::list<std::string> LRU_t;
+        LRU_t lru;
+        
+        struct M_LRU_element_t
+        {
+            M_LRU_element_t(const std::string &);
+            M_LRU_element_t(const std::string *);
+            M_LRU_element_t(const std::string *, const LRU_t::iterator &);
+            const std::string *key;
+            LRU_t::iterator lit;
+        };
+        struct KeyHasher
+        {
+            size_t operator()(const M_LRU_element_t &l) const;
+        };
+
+        struct KeyEquals 
+        {
+            bool operator()(const M_LRU_element_t &l1, const M_LRU_element_t &l2) const;
+        };
+        
+        typedef std::unordered_set<M_LRU_element_t, KeyHasher, KeyEquals> M_LRU_t;
+        M_LRU_t m_lru;   // the LRU entries as a hash table
+        
+        /* The do-not-evict list stuff */
+        struct DNEElement
+        {
+            DNEElement(const LRU_t::iterator &);
+            LRU_t::iterator key;
+            uint refCount;
+        };
+        
+        struct DNEHasher
+        {
+            size_t operator()(const DNEElement &d) const;
+        };
+        
+        struct DNEEquals
+        {
+            bool operator()(const DNEElement &d1, const DNEElement &d2) const;
+        };
+        
+        typedef std::unordered_set<DNEElement, DNEHasher, DNEEquals> DNE_t;
+        DNE_t doNotEvict;
+        void addToDNE(const LRU_t::iterator &key);
+        void removeFromDNE(const LRU_t::iterator &key);
+        boost::mutex lru_mutex;   // protects the main cache structures & the do-not-evict set
+        
+        Downloader downloader;
         
 };
 
+
+
 }
 
 #endif
diff --git a/src/CloudStorage.h b/src/CloudStorage.h
index 14d8924e6..43e69af12 100644
--- a/src/CloudStorage.h
+++ b/src/CloudStorage.h
@@ -10,6 +10,7 @@ namespace storagemanager
 class CloudStorage
 {
     public:
+        /* These behave like syscalls.  return code -1 means an error, and errno is set */
         virtual int getObject(const std::string &sourceKey, const std::string &destFile) = 0;
         virtual int putObject(const std::string &sourceFile, const std::string &destKey) = 0;
         virtual void deleteObject(const std::string &key) = 0;
diff --git a/src/Config.cpp b/src/Config.cpp
index 3cac02ac7..45e7df3a3 100644
--- a/src/Config.cpp
+++ b/src/Config.cpp
@@ -7,6 +7,9 @@
 
 #include <stdlib.h>
 #include <vector>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 using namespace std;
 
@@ -30,7 +33,7 @@ Config * Config::get()
     return inst;
 }
 
-Config::Config()
+Config::Config() : die(false)
 {
     /* This will search the current directory,
        then $COLUMNSTORE_INSTALL_DIR/etc,
@@ -59,7 +62,51 @@ Config::Config()
     }
     if (filename.empty())
         throw runtime_error("Config: Could not find the config file for StorageManager");
-        
+    
+    reloadInterval = boost::posix_time::seconds(60);
+    last_mtime = {0, 0};
+    reload();
+    reloader = boost::thread([this] { this->reloadThreadFcn(); });
+}
+
+Config::~Config()
+{
+    die = true;
+    reloader.interrupt();
+    reloader.join();
+}
+
+void Config::reloadThreadFcn()
+{
+    while (!die)
+    {
+        try
+        {
+            reload();
+            boost::this_thread::sleep(reloadInterval);
+        }
+        catch (boost::property_tree::ini_parser_error &e)
+        {
+            // log the error.  how to log things now?
+        }
+        catch (boost::thread_interrupted)
+        {}
+    }
+}
+
+void Config::reload()
+{
+    struct stat statbuf;
+    int err = stat(filename.c_str(), &statbuf);
+    if (err)
+        // log something
+        return;
+    if ((statbuf.st_mtim.tv_sec == last_mtime.tv_sec) && (statbuf.st_mtim.tv_nsec == last_mtime.tv_nsec))
+        return;
+    last_mtime = statbuf.st_mtim;
+    
+    boost::unique_lock<boost::mutex> s(mutex);
+    contents.clear();
     boost::property_tree::ini_parser::read_ini(filename, contents);
 }
 
@@ -86,7 +133,10 @@ string expand_numbers(const boost::smatch &match)
 string Config::getValue(const string &section, const string &key) const
 {
     // if we care, move this envvar substition stuff to where the file is loaded
+    boost::unique_lock<boost::mutex> s(mutex);
     string ret = contents.get<string>(section + "." + key);
+    s.unlock();
+    
     boost::regex re("\\$\\{(.+)\\}");
     
     ret = boost::regex_replace(ret, re, use_envvar);
diff --git a/src/Config.h b/src/Config.h
index 56e185f38..8f103c53b 100644
--- a/src/Config.h
+++ b/src/Config.h
@@ -3,6 +3,10 @@
 #define CONFIG_H_
 
 #include <boost/property_tree/ptree.hpp>
+//#include <boost/thread/mutex.hpp>
+#include <boost/thread.hpp>
+#include <sys/types.h>
+
 #include <string>
 
 
@@ -12,14 +16,23 @@ class Config : public boost::noncopyable
 {
     public:
         static Config *get();
+        virtual ~Config();
         
         std::string getValue(const std::string &section, const std::string &key) const;
         
     private:
         Config();
         
+        void reload();
+        void reloadThreadFcn();
+        struct ::timespec last_mtime;
+        mutable boost::mutex mutex;
+        boost::thread reloader;
+        boost::posix_time::time_duration reloadInterval;
+        
         std::string filename;
         boost::property_tree::ptree contents;
+        bool die;
 };
 
 }
diff --git a/src/Downloader.cpp b/src/Downloader.cpp
new file mode 100644
index 000000000..65819e193
--- /dev/null
+++ b/src/Downloader.cpp
@@ -0,0 +1,119 @@
+#include "Downloader.h"
+#include "Config.h"
+#include <string>
+#include <errno.h>
+
+using namespace std;
+namespace storagemanager
+{
+
+Downloader::Downloader()
+{
+    storage = CloudStorage::get();
+    string sMaxDownloads = Config::get()->getValue("ObjectStorage", "max_concurrent_downloads");
+    maxDownloads = stoi(sMaxDownloads);
+    if (maxDownloads == 0)
+        maxDownloads = 20;
+}
+
+Downloader::~Downloader()
+{
+}
+
+void Downloader::download(const vector<const string *> &keys)
+{
+    uint counter = keys.size();
+    boost::condition condvar;
+    boost::mutex m;
+    DownloadListener listener(&counter, &condvar, &m);
+    
+    boost::shared_ptr<Download> dls[keys.size()];
+    bool inserted[keys.size()];
+    Downloads_t::iterator iterators[keys.size()];
+    
+    uint i;
+    
+    for (const string *key : keys)
+        dls[i].reset(new Download(key, this));
+    
+    boost::unique_lock<boost::mutex> s(download_mutex);
+    for (i = 0; i < keys.size(); i++)
+    {
+        auto &dl = dls[i];
+        pair<Downloads_t::iterator, bool> ret = downloads.insert(dl);
+        iterators[i] = ret.first;
+        inserted[i] = ret.second;
+        
+        if (inserted[i])
+        {
+            dl->listeners.push_back(&listener);
+            downloaders->addJob(dl);
+        }
+        else
+            (*iterators[i])->listeners.push_back(&listener);
+    }
+    s.unlock();
+    
+    // wait for the downloads to finish
+    boost::unique_lock<boost::mutex> dl_lock(m);
+    while (counter > 0)
+        condvar.wait(dl_lock);
+    dl_lock.unlock();
+    
+    // remove the entries inserted by this call
+    s.lock();
+    for (i = 0; i < keys.size(); i++)
+        if (inserted[i])
+            downloads.erase(iterators[i]);
+
+    // TODO: check for errors & propagate
+}
+
+void Downloader::setDownloadPath(const string &path)
+{
+    downloadPath = path;
+}
+
+inline const string & Downloader::getDownloadPath() const
+{
+    return downloadPath;
+}
+           
+/* The helper fcns */
+Downloader::Download::Download(const string *source, Downloader *dl) : key(source), dler(dl), dl_errno(0)
+{
+}
+
+void Downloader::Download::operator()()
+{
+    CloudStorage *storage = CloudStorage::get();
+    int err = storage->getObject(*key, dler->getDownloadPath() + *key);
+    if (err != 0)
+        dl_errno = errno;
+        
+    for (auto &listener : listeners)
+        listener->downloadFinished();
+}
+
+Downloader::DownloadListener::DownloadListener(uint *counter, boost::condition *condvar, boost::mutex *m) : count(counter), cond(condvar), mutex(m)
+{
+}
+
+void Downloader::DownloadListener::downloadFinished()
+{
+    boost::unique_lock<boost::mutex> u(*mutex);
+    if (--(*count) == 0)
+        cond->notify_all();
+}
+
+inline size_t Downloader::DLHasher::operator()(const boost::shared_ptr<Download> &d) const
+{
+    return hash<string>()(*(d->key));
+}
+
+inline bool Downloader::DLEquals::operator()(const boost::shared_ptr<Download> &d1, const boost::shared_ptr<Download> &d2) const
+{
+    return (*(d1->key) == *(d2->key));
+}
+
+}
diff --git a/src/Downloader.h b/src/Downloader.h
new file mode 100644
index 000000000..d52b3073d
--- /dev/null
+++ b/src/Downloader.h
@@ -0,0 +1,73 @@
+#ifndef DOWNLOADER_H_
+#define DOWNLOADER_H_
+
+#include "ThreadPool.h"
+#include "CloudStorage.h"
+#include <unordered_set>
+#include <vector>
+#include <string>
+
+#include <boost/shared_ptr.hpp>
+#include <boost/scoped_ptr.hpp>
+#include <boost/thread/mutex.hpp>
+#include <boost/thread/condition.hpp>
+
+namespace storagemanager
+{
+
+class Downloader
+{
+    public:
+        Downloader();
+        virtual ~Downloader();
+        
+        void download(const std::vector<const std::string *> &keys);
+        void setDownloadPath(const std::string &path);
+        const std::string & getDownloadPath() const;
+        
+    private:
+        uint maxDownloads;
+        std::string downloadPath;
+    
+        class DownloadListener
+        {
+        public:
+            DownloadListener(uint *counter, boost::condition *condvar, boost::mutex *m);
+            void downloadFinished();
+        private:
+            uint *count;
+            boost::condition *cond;
+            boost::mutex *mutex;
+        };
+    
+        struct Download : public ThreadPool::Job
+        {
+            Download(const std::string *source, Downloader *);
+            void operator()();
+            Downloader *dler;
+            const std::string *key;
+            int dl_errno;   // to propagate errors from the download job to the caller
+            std::vector<DownloadListener *> listeners;
+        };
+    
+        struct DLHasher
+        {
+            size_t operator()(const boost::shared_ptr<Download> &d) const;
+        };
+        
+        struct DLEquals
+        {
+            bool operator()(const boost::shared_ptr<Download> &d1, const boost::shared_ptr<Download> &d2) const;
+        };
+    
+        typedef std::unordered_set<boost::shared_ptr<Download>, DLHasher, DLEquals> Downloads_t;
+        Downloads_t downloads;
+        boost::mutex download_mutex;
+        
+        boost::scoped_ptr<ThreadPool> downloaders;
+        CloudStorage *storage;
+};
+
+}
+
+#endif
diff --git a/src/ThreadPool.cpp b/src/ThreadPool.cpp
index 9cf5d8abf..7b7f7278b 100644
--- a/src/ThreadPool.cpp
+++ b/src/ThreadPool.cpp
@@ -1,8 +1,5 @@
 
-
-
 #include "ThreadPool.h"
-#include <boost/thread/mutex.hpp>
 
 using namespace std;
 
@@ -18,36 +15,75 @@ ThreadPool::ThreadPool() : maxThreads(1000), die(false), threadsWaiting(0)
 
 ThreadPool::ThreadPool(uint num_threads) : maxThreads(num_threads), die(false), threadsWaiting(0)
 {
+    pruner = boost::thread([this] { this->pruner_fcn(); } );
 }
 
 ThreadPool::~ThreadPool()
 {
-    boost::mutex::scoped_lock s(m);
+    boost::unique_lock<boost::mutex> s(m);
     die = true;
     jobs.clear();
     jobAvailable.notify_all();
     s.unlock();
     
-    for (uint i = 0; i < threads.size(); i++)
-        threads[i]->join();
+    threads.join_all();
+    pruner.interrupt();
+    pruner.join();
 }
 
 void ThreadPool::addJob(const boost::shared_ptr<Job> &j)
 {
-    boost::mutex::scoped_lock s(m);
+    boost::unique_lock<boost::mutex> s(m);
     jobs.push_back(j);
     // Start another thread if necessary
     if (threadsWaiting == 0 && threads.size() < maxThreads) {
-        boost::shared_ptr<boost::thread> thread(new boost::thread(Runner(this)));
-        threads.push_back(thread);
+        boost::thread *thread = threads.create_thread([this] { this->processingLoop(); });
+        s_threads.insert(thread);
     }
     else
         jobAvailable.notify_one();
 }
 
+void ThreadPool::pruner_fcn()
+{
+    while (!die)
+    {
+        prune();
+        try {
+            boost::this_thread::sleep(idleThreadTimeout);
+        }
+        catch(boost::thread_interrupted)
+        {}
+    }
+}
+
+void ThreadPool::prune()
+{
+    boost::unique_lock<boost::mutex> s(m);
+    set<boost::thread *>::iterator it, to_remove;
+    it = s_threads.begin();
+    while (it != s_threads.end())
+    {
+        if ((*it)->joinable())
+        {
+            (*it)->join();
+            threads.remove_thread(*it);
+            to_remove = it++;
+            s_threads.erase(to_remove);
+        }
+        else
+            ++it;
+    }
+}
+
+void ThreadPool::setMaxThreads(uint newMax)
+{
+    maxThreads = newMax;
+}
+
 void ThreadPool::processingLoop()
 {
-    boost::mutex::scoped_lock s(m, boost::defer_lock);
+    boost::unique_lock<boost::mutex> s(m, boost::defer_lock);
     
     while (!die)
     {
@@ -55,8 +91,10 @@ void ThreadPool::processingLoop()
         while (jobs.empty() && !die) 
         {
             threadsWaiting++;
-            jobAvailable.wait(s);
+            bool timedout = !jobAvailable.timed_wait<>(s, idleThreadTimeout);
             threadsWaiting--;
+            if (timedout)
+                return;
         }
         if (die)
             return;
diff --git a/src/ThreadPool.h b/src/ThreadPool.h
index 13b69f234..8669e7c1f 100644
--- a/src/ThreadPool.h
+++ b/src/ThreadPool.h
@@ -2,8 +2,8 @@
 #ifndef SM_THREADPOOL_H_
 #define SM_THREADPOOL_H_
 
-#include <list>
 #include <deque>
+#include <set>
 #include <boost/thread.hpp>
 #include <boost/thread/condition.hpp>
 
@@ -25,6 +25,7 @@ class ThreadPool : public boost::noncopyable
         };
         
         void addJob(const boost::shared_ptr<Job> &j);
+        void setMaxThreads(uint newMax);
 
     private:
         struct Runner {
@@ -38,10 +39,16 @@ class ThreadPool : public boost::noncopyable
         uint maxThreads;
         bool die;
         int threadsWaiting;
-        std::vector<boost::shared_ptr<boost::thread> > threads;
+        boost::thread_group threads;
+        std::set<boost::thread *> s_threads;
         boost::condition jobAvailable;
         std::deque<boost::shared_ptr<Job> > jobs;
         boost::mutex m;
+        
+        const boost::posix_time::time_duration idleThreadTimeout = boost::posix_time::seconds(60);
+        boost::thread pruner;
+        void pruner_fcn();
+        void prune();
 };
 
 
diff --git a/storagemanager.cnf b/storagemanager.cnf
index 212a6ae3d..d09f205c6 100644
--- a/storagemanager.cnf
+++ b/storagemanager.cnf
@@ -2,7 +2,7 @@
 service = S3
 object_size = 5M
 metadata_path = ${HOME}/storagemanager/metadata
-
+max_concurrent_downloads = 20
 
 [S3]
 region = us-west-1