none
Torn_Page_Detection vs Checksum as Page Verifications

    Question

  • Any have experiences with the CHECKSUM database page verification (good or bad)?

    My concern is that each would be ideal for certain situations, but none have been documented. Another concern is that CHECKSUM may not catch all the exceptions that TORN_PAGE would, and vice versa.

    If I had to guess, CHECKSUM introduces a minimal CPU overhead that could be noticed with larger recordsets, but offers more overall protection.

    From Books Online:

    CHECKSUM

    Calculates a checksum over the contents of the whole page and stores the value in the page header when a page is written to disk. When the page is read from disk, the checksum is recomputed and compared to the checksum value stored in the page header. If the values do not match, error message 824 (indicating a checksum failure) is reported to both the SQL Server error log and the Windows event log. A checksum failure indicates an I/O path problem. To determine the root cause requires investigation of the hardware, firmware drivers, BIOS, filter drivers (such as virus software), and other I/O path components.

    TORN_PAGE_DETECTION

    Saves a specific bit for each 512-byte sector in the 8-kilobyte (KB) database page and stored in the database page header when the page is written to disk. When the page is read from disk, the torn bits stored in the page header are compared to the actual page sector information. Unmatched values indicate that only part of the page was written to disk. In this situation, error message 824 (indicating a torn page error) is reported to both the SQL Server error log and the Windows event log. Torn pages are typically detected by database recovery if it is truly an incomplete write of a page. However, other I/O path failures can cause a torn page at any time.

    Monday, November 06, 2006 6:54 PM

Answers

  • From the horses' mouth:
    http://blogs.msdn.com/sqlserverstorageengine/archive/2006/06/29/Enabling-CHECKSUM-in-SQL2005.aspx


    Tuesday, November 07, 2006 8:38 AM