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title Check Disk Input and Output Subsystem for IO Delay Problems | Microsoft Docs
ms.custom
ms.date 06/13/2017
ms.prod sql-server-2014
ms.reviewer
ms.technology security
ms.topic conceptual
helpviewer_keywords
Best Practices [Database Engine]
ms.assetid 23863340-d8e0-48d6-928b-462745885d37
author MikeRayMSFT
ms.author mikeray
manager craigg

Check Disk Input and Output Subsystem for IO Delay Problems

This rule checks the event log for error message 833. This message indicates that [!INCLUDEssNoVersion] 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 [!INCLUDEssNoVersion] and indicates a problem with the disk I/O subsystem. Delays this long can severely damage the performance of your [!INCLUDEssNoVersion] 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 [!INCLUDEssNoVersion] 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

MSSQLSERVER_833

Microsoft Knowledge Base article 897284

SQL Server I/O Basics, Chapter 2