将Azure blob的内容下载为文本字符串花费的时间太长

我正在开发一个应用程序

1. 使用简单的HTTP网页(REST方法)从本地机器上传。csv文件到Azure blob存储

2. 一旦，csv文件上传，我获取流以更新我的数据库

. csv文件大约30 MB，上传到blob需要2分钟，但是读取流需要30分钟。能否提供输入以提高速度?下面是用来从文件中读取流的代码片段:https://azure.microsoft.com/en-in/documentation/articles/storage-dotnet-how-to-use-blobs/

public string GetReadData(string filename)
        {
            // Retrieve storage account from connection string.
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(System.Web.Configuration.WebConfigurationManager.AppSettings["StorageConnectionString"]);
            // Create the blob client.
            CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
            // Retrieve reference to a previously created container.
            CloudBlobContainer container = blobClient.GetContainerReference(System.Web.Configuration.WebConfigurationManager.AppSettings["BlobStorageContainerName"]);
            // Retrieve reference to a blob named "filename"
            CloudBlockBlob blockBlob2 = container.GetBlockBlobReference(filename);
            string text;
            using (var memoryStream = new MemoryStream())
            {
                blockBlob2.DownloadToStream(memoryStream);
                text = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());
            }
            return text;
        }