Serialize List and Big Object For Redis Cache

Question

I have an ASP.NET e-commerce application. My application has big traffic and I have to use caching system. I switch my cache mechanism from in-memory (memcache) to redis (distributed cache) because I have five servers.

There was no problem with memcache but I have a problem now after to switch redis. For example I serialize my list and it take about 4-5 MB but when I read it from redis-cli so it's fetched very slowly, about 5 seconds and my application raises timeout exception therefore.

I read that "do not store big data in redis". In other hand I use output cache and session cache with MVC for redis there is no problem. Should I use BinarySerializer or what? How can I store big objects in redis cache?

Thanks in advice.

    public List<ProdFilter> GetAll(int prodFeatureGroupId)
    {
        var cacheKey = string.Format("{0}_{1}_{2}",
                            "ProductRepository",
                            "GetAll",
                            prodFeatureGroupId);
        var isExists = _cache.Contains(cacheKey) && Const.CacheIsActive;

        List<ProdFilter> obj;
        if (isExists)
        {
            obj = _cache.Get<List<ProdFilter>>(cacheKey);
        }
        else
        {
            obj = _db.ProdFilters
                    .Where(x => x.ProdFilterGroupId == prodFeatureGroupId)
                    .ToList();
            _cache.Add(cacheKey, obj);
        }

        return obj;
    }

    //my cache methods
    private void Create()
    {
        if (null == _db)
        {
            ConfigurationOptions option = new ConfigurationOptions();
            option.Ssl = false;
            option.EndPoints.Add(_host, _port);
            var connect = ConnectionMultiplexer.Connect(option);

            _db = connect.GetDatabase();
        }
    }

    public void Add<T>(string key, T obj)
    {
        var data = Serialize(obj);
        _db.StringSet(key, data);
    }

    public void Set<T>(string key, T obj)
    {
        Add(key, obj);
    }

    public T Get<T>(string key)
    {
        var val = _db.StringGet(key);

        return Deserialize<T>(val);
    }

    // my serialize helper
    public static byte[] Serialize(object o)
    {
        if (o == null)
        {
            return null;
        }

        BinaryFormatter binaryFormatter = new BinaryFormatter();

        using (MemoryStream memoryStream = new MemoryStream())
        {
            binaryFormatter.Serialize(memoryStream, o);
            byte[] objectDataAsStream = memoryStream.ToArray();
            return objectDataAsStream;
        }
    }

    public static T Deserialize<T>(byte[] stream)
    {
        if (stream == null)
            return (default(T));

        BinaryFormatter binaryFormatter = new BinaryFormatter();

        using (MemoryStream memoryStream = new MemoryStream(stream))
        {
            T result = (T)binaryFormatter.Deserialize(memoryStream);
            return result;
        }
    }