Primary and extended partions on the same physical drive using Windows 2003

Posted on 2007-10-17
Last Modified: 2010-07-27
What are the performance differences between Primary and extended partions on the same physical drive and any other benefits....Fior example you are going to 2003 Enterprise on the C:\ and the  page file on d:\..But the d:\ is a primary partition not an extended partition..the C: and D: are part of a mirror.....but the d:....    is a primary partition ???
Question by:handymanaly
    LVL 95

    Expert Comment

    by:Lee W, MVP
    Partitions are just a "hard limit" of sorts on data usage.  Putting the page file on a partition that is part of the same physical disk or RAID set will not show any significant benefit - you would need to put the pagefile on another set of disk spindles to see any kind of noticeable benefit.

    Author Comment

    Is there any benefit at all  to doing this???  
    LVL 87

    Expert Comment

    There is no performance difference between primary or extended (logical) partitions. Windows can only access 4 primary partitions per drive, while you can have up to 127 logical partitions within an extended partition (I'm not sure whether the 4 primary partitions limit still is true for Vista).

    It is still better to have the pagefile on another partition than the OS is on. The advantage here is not performance, but rather separation of the OS from temporary data.
    LVL 9

    Expert Comment

    rindi: you said
    >> The advantage here is not performance, but rather separation of the OS from temporary data.
    I don't follow what that buys you?
    LVL 9

    Expert Comment

    ... are you perhaps referring to this approach reducing writes to the OS' partition (because the pagefile is maintained elsewhere) thereby reducing the potential for corruption to the MFT?
    LVL 70

    Accepted Solution

    A couple of comments ...

    First, r.e. "... Is there any benefit at all to doing this???" ==>  Yes.  Not necessarily for isolating the page file; but to separate your system from the data.   If you keep the system on one partition, and all of your data on another; then if you ever have a problem that requires restoring the system from an earlier image (or rebuilding it entirely), the data will not be impacted.   I would always use Primary partitions rather than extended partitions; as this keeps the partition structure info in the MBR => extended data is retained in the associated primary partition, which requires a bit of additional processing; and if there are multiple extended partitions and the primary partition gets corrupted, you can lose all of the extended partitions.   The only reason to use extended partitions is if you need more than 4 partitions on the drive.

    Second, r.e. rindi's comment "... I'm not sure whether the 4 primary partitions limit is still true for Vista..." ==>  The 4 primary partitions limit is a function of the Master Boot Record (MBR) structure, which can only support 4 partition ID records.   This limit was removed with Windows 2003 when Microsoft supported GPT partitions [GUID Partition Table => Globally Unique IDentifier Partition Table].   The GPT structure allows essentially unlimited partitions; although Microsoft's implementation restricts it to 128 partitions.    Vista supports both MBR and GPT disks ==> although both Server 2003 and Vista cannot boot from a GPT volume unless the system supports Intel's Extensible Firmware Interface.   So the answer to your question is that Vista does not have this limit with GPT disks;  but that was not something new to Vista.   You can read a bit more about this at

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