• About Running Chkdsk in Read-only Mode
  • Variable 3: Hardware Issues




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    Variable 3: Hardware Issues


    Hardware issues also affect how long it takes for Chkdsk to run. The variables include the available memory, CPU speed, I/O throughput (fibre channel or Small Computer System Interface [SCSI]), disk RPM speed, and others.

    Variable 4: The Chkdsk Settings


    If you use the /r command-line switch, Chkdsk has to read and verify every sector on the volume, which adds significantly to the time that it takes for large volumes.

    If you do not use the /r option, the biggest time issue on a particular hardware platform is the number of files and folders that are on the volume, instead of the absolute size of the volume. For example, a 50-GB volume that has only one or two large database files might take only seconds for Chkdsk to run. On the other hand, running Chkdsk on even a relatively small volume might require hours if the volume has hundreds of thousands or even millions of small files — regardless of whether you specify the /r option.


    About Running Chkdsk in Read-only Mode


    The best way to predict how long Chkdsk will take to run on a particular volume is to actually do a trial run in read-only mode during a period of low system usage. However, you must use this technique with great care for the following reasons:

    • In read-only mode, Chkdsk quits before it completes the first three phases if it finds inconsistencies, and Chkdsk is prone to falsely reporting errors when it runs in read-only mode. For example, Chkdsk may report disk corruption if NTFS happens to modify areas of a disk while Chkdsk is examining the disk. For correct verification, a volume must be static, and the only way to guarantee a static state is to lock the volume. Chkdsk locks the volume only if you specify the /f command-line switch (or the /r option, which implies /f). You may have to run Chkdsk more than one time to get Chkdsk to complete all its passes in read-only mode.

    • Chkdsk is both CPU intensive and disk intensive. The time that it takes to run Chkdsk is affected by how much load is on the system and whether Chkdsk runs online or during the Windows 2000 startup sequence. Which factor becomes the bottleneck depends on the hardware configuration, but high CPU usage or heavy disk I/O while Chkdsk is running in read-only mode increases the Chkdsk running time. Also, Autochk.exe runs in a different environment from that of Chkdsk.exe. Running Autochk.exe gives Chkdsk exclusive use of CPU and I/O resources, but it also prevents Chkdsk from using virtual memory. Although you might expect Autochk.exe to run faster than Chkdsk.exe, Autochk.exe may actually take longer if the computer has relatively little available RAM.

    • Fixing corruption adds to the time that it takes. In read-only mode, Chkdsk runs until it is complete only if Chkdsk does not find any significant corruption. If a disk shows only minor corruption, fixing the problems will not add much to the time that it takes just to run Chkdsk. But if Chkdsk finds major damage — for example, from a serious hardware failure — the time will increase in proportion to the number of damaged files that Chkdsk must repair. In extreme cases, this can more than double the time that it takes for Chkdsk to run.



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