.NET IIS App没有磁盘空间

我有一个运行多个应用程序的IIS服务器。 当我检查该服务器上的C：\驱动器上的可用空间时，它表示20GB空闲。 但我仍然得到以下堆栈跟踪：

[IOException: There is not enough space on the disk. ] System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) +7717304 System.IO.Directory.InternalCreateDirectory(String fullPath, String path, DirectorySecurity dirSecurity) +7569557 System.IO.Directory.CreateDirectory(String path, DirectorySecurity directorySecurity) +150 batchprocessor.btnUpload_Click(Object sender, EventArgs e) +979 System.Web.UI.WebControls.LinkButton.OnClick(EventArgs e) +111 System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) +79 System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +175 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565 

有没有单独的配额？