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Should the paging file be moved from C: drive?

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Should the paging file be moved from C: drive to another drive? This was the question I received today and thought I’d share my response to this.

There is no general answer for all situations, so this question needs more information about the environment. This is why you will not (and should not) find any official articles answering this question in any generalized form.

First, the paging file must be able to accommodate the crash dump settings. Windows Server 2003 requires the paging file to be on the system partition and be large enough to accommodate the crash dump setting. Windows Server 2008 and later allows the paging file to be on other direct attached drives when accommodating a crash dump. Complete memory dumps requires the paging file to be 1xRAM + 1 MB, Kernel memory dumps vary based on the amount of kernel memory usage such as pool paged and pool non-paged sizes estimating roughly 100 MB for every 1 GB of RAM. Small dumps require about 1 MB of a paging file.

Second, it depends on the amount of system committed memory that has been promised. The system commit limit is the size of RAM + paging files. It must always be larger than the system commit charge. The system commit charge will vary based on actual usage. With that said, committed memory doesn’t *not* mean that the paging file is actually being used. If the system commit charge is very large, but little of it is “touched”, then having a paging file on a slow disk drive is fine because the paging file is not really being used – just there to accommodate the commit charge *if* it happens to become “touched” memory.

Third, assuming the C: drive is a slow drive and that the system commit charge is greater than RAM, and the committed memory is actually “touched”, then the performance of the disk where the paging file is at is important. A page is 4 KB, so a sustained 1000 pages/sec (hard page faults) is 4 MB per second. Most 7200 RPM disk drives can handle 10 MB per second for reference.

If paging files are defined across multiple disks, then the paging file that is available first is used – meaning this is a load balanced situation which can help. Ultimately, if the paging file is *really* being used this much, then just add more RAM or place the paging file on a SSD.

In short, moving the paging file really depends on how much the paging file(s) are really being used (touched memory), the crash dump settings, version of the operating system, the system commit charge at peak, and disk drive performance.

Comments

  • Anonymous
    January 01, 2003
    In general, YES, when possible! ALWAYS move the page file to another physical disk, whenever possible. Basically, any paging that happnes OFF the "system disk" is good, BUT, the disk that holds the page file must be a disk of decent speed (7200 rpm or better - i.e., SSD, 15k SATA, etc.), and of adequate size. Additionally, whatever disk drive controller (embedded or separate bus-based controller), for the drive where the page file will reside, must be of adequate performance. And NO, if you have only separate "logical partions/drives," DO NOT MOVE THE PAGE FILE, because it will not improve performance. Example: you have one RAID 5 array of 3 disks, with D:, E:, F: partitions of different size; it would not imprive anything to move the page file from C: to D:, E: or F:, because ALL your partitions in this case are on the SAME PHYSICAL DISK AREA (3 RAIDed drives).

  • Anonymous
    January 01, 2003
    Hi Eugene, Moving a page file to a location to a volume that is not replicated would be dependent on the replication software's behavior. If it understands page files and other related system files. For example, backup software generally will not backup a page file.

  • Anonymous
    June 11, 2013
    Hi TNJMAN, Not all situations require moving the paging file to another disk drive. I've tried to explain this in my article. It really depends on the memory usage patterns of the system. You cannot generalize this for all situations. Some systems don't even need a paging file, while others must have one. Even ones that have a paging file might not even be using it. With that said, I agree with your other comments that placing a paging file on the same physical spindles is not beneficial.

  • Anonymous
    October 05, 2013
    What about in cases of disk snapshots and disk replication -- does the page file not represent ephemera and should be moved to a volume which is then not replicated?

  • Anonymous
    October 28, 2013
    After reading some of these post I must say that there definitely seems to be some differences of opinion. First assess what the page file should be in size and to see what and IF you need one at all. Microsoft has couple decent articles or running perfmon and crunching some counters to figure out what your page file size should be. Not all machines use a swap file the same. A web server and an SQL server on the same physical hardware perform differently and as such use memory and your swap file differently. Second. If you can move the page file off, and you are ok with not being able to get full kernel dumps for your BSODs than do so. If you cannot get spate physical spindles (best option) you will see some minor performance increase in moving your swap file to a separate partition on the same disk (array), at least from a fragmentation perspective. Here are a couple interesting articles from MS regarding swap files: support.microsoft.com/.../2160852 support.microsoft.com/.../889654 All in all you need to 1st figure what you need before you ask yourself where to move it.

  • Anonymous
    October 28, 2013
    I want to move my pagefile out of C: because my C: partition is on a Solid State Disc, and any SSD has a limited life with respect to the number of WRITE operations. In Windows 7 (64bit) I set up a pagefile on a second (rotating) disc, and then tried to remove the Pagefile from C: on the SSD. This got me a message that "if the pagefile on C; is less than 400MB, then a dump of the Crash data when there is a System failure may be impossible". Is this a serious problem if a Crash occurs? The situation re SSD appears to be, if no pagefile on C: (on SSD), then Crash resilience is reduced (? seriously); but if there is a pagefile there then a crash is more likely to occur due to limited number of Writes on SSD. Which is the lesser risk?

  • Anonymous
    November 11, 2013
    Chris,  That shouldn't be an issue if you disable the crash dumps (for the average user they really serve no purpose).

  • Anonymous
    April 10, 2014
    The comment has been removed

  • Anonymous
    August 01, 2014
    Hi ,

    I checked a production virtual server and found that C: drive space is low. Please find details below :

    OS name : MS windows server 2003 Enterprise x64 edition.
    version : 5.2.3790 service pack 2 build 3790
    total physical memory : 7GB
    total virtual memory : 17 GB
    pagefile space : 10GB

    I have another two drive and have suffecient space.

    Please suggest can I move pagefile to another drive or should i increase the C: drive space.

  • Anonymous
    January 29, 2015
    Even with logical volumes on Raided drives, In the case of low drive space on C: shouldn't the page file be moved?

    e.g.
    C:OS = 5gb available
    D:Data = 420gb available

    So, even though they are a RAID on the same spindles, I should move my page file to D:, correct?

  • Anonymous
    April 22, 2015
    The comment has been removed

  • Anonymous
    May 29, 2015
    My server has 144GB of RAM, and only seems to be using 12GB paging about half... Should I turn off paging?

  • Anonymous
    July 22, 2015
    I have a system that is a VMWare VM, the Drives are stored on a NAS, and the VM runs on a Dell poweredge 840. The 840 has a USB drive that VMWare runs from, and has a single 1TB drive in it that I use dedicated for shadow copies. I tried to move the swap file to the same drive , but when I did the backup stopped working. I eliminated all other page files, so I'm wondering if there's something I'm missing? My goal is to not have to swap/page across the network to the NAS that the drives are stored on, but needless to say, I need backup to work too! Any recommendations are appreciated!

  • Anonymous
    January 03, 2016
    Re Pagefile:
    My laptop is a Samsung Series 7 NP700z5c.
    Can I use the now redundant SanDisk iSSD just for Pagefile?
    And if yes, do I make the pagefile equal to the size of the iSSD?

    I have changed the HDD to SSD, and the built-in iSSD (was used for speed increase) is no longer used.
    OS
    Windows 7 Professional 64-bit SP1
    CPU
    Intel Core i7 3615QM @ 2.30GHz 51 °C
    Ivy Bridge 22nm Technology
    RAM
    8.00GB Dual-Channel DDR3 @ 798MHz (11-11-11-28)
    Storage
    232GB Samsung SSD 850 EVO 250G (SSD) as 'C' drive
    7GB SanDisk iSSD P4 8GB (SSD) as 'F' drive