---
title: "Check disk IO subsystem for IO delay problems"
description: Learn how to enable a policy to check the disk IO subsystem for IO delay problems by checking the event log for error message 833 for Policy-Based Management with SQL Server. 
ms.custom: seo-lt-2019
ms.date: "03/14/2017"
ms.prod: sql
ms.prod_service: "database-engine"
ms.reviewer: ""
ms.technology: security
ms.topic: conceptual
helpviewer_keywords: 
  - "Best Practices [Database Engine]"
ms.assetid: 23863340-d8e0-48d6-928b-462745885d37
author: VanMSFT
ms.author: vanto
---
# Check Disk Input and Output Subsystem for IO Delay Problems
[!INCLUDE[appliesto-ss-xxxx-xxxx-xxx-md](../../includes/appliesto-ss-xxxx-xxxx-xxx-md.md)]
  This rule checks the event log for error message 833. This message indicates that [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] has issued a read or write request from disk, and that the request has taken longer than 15 seconds to return. This error is reported by [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] and indicates a problem with the disk I/O subsystem. Delays this long can severely damage the performance of your [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] environment.  
  
## Best Practices Recommendations  
 Troubleshoot this error by examining the system event log for hardware-related error messages. Also, examine hardware-specific logs if they are available.  
  
 Use Performance Monitor to examine the following counters:  
  
-   Average Disk Sec/Transfer  
  
-   Average Disk Queue Length  
  
-   Current Disk Queue Length  
  
 For example, the Average Disk Sec/Transfer time on a computer that is running [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] is typically less than 15 milliseconds. If the Average Disk Sec/Transfer value increases, this indicates that the disk I/O subsystem is not optimally keeping up with the I/O demand.  
  
## For More Information  
   
  
 [Microsoft Knowledge Base article 897284](https://go.microsoft.com/fwlink/?linkid=117743)  
  
 [SQL Server I/O Basics, Chapter 2](/previous-versions/sql/sql-server-2005/administrator/cc917726(v=technet.10))