Partition portion of External HD for System Files Backup

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  1. Posts : 80
    windows 10 64 bit h20

    Partition portion of External HD for System Files Backup

    Current Windows Version 2004 (OS Build 1904.329)

    I have a secondary 3TB External USB HD. Once formatted leaves me with 2.72 TB of storage. What I would like to do is have two partitions on this physical drive. Logical Drive K which would have about 600gb and that would leave Logical Drive L with a 2.10 TB storage. That part is easy to achieve. My question is can I be backing up the system files on Drive K while I am adding data files to Drive L?
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  2. Posts : 1,867
    Windows 10 Pro 2004 20H1

    You can.

    Just not at the same time.

    A disk imaging program will image the entire drive unless you have the hard drive partitioned as well.

    Then you can image by partition.

    You could also have Windows on one drive, and your personal data and apps on another drive.

    This would make it easy to clean install Windows, and not touch anything else.
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  3. Posts : 12,468
    Win10 Version 21H2 Pro and Home, Win11 Pro

    Have to agree with OldNavyGuy [once was one of those] but would ask about the need for a Logical drive since only 2 partitions are involved [can have up to 4]. I'd go with 2 Primary partitions and neither one Active [not needed if not a boot drive].
    Primary Partition, Logical Partition and Extended Partition (Disk Partition Basic)
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  4. Posts : 2,803
    Windows 11 Pro, 22H2


    Your description is a little bit vague but here goes an attempt at an answer with some more details for you.

    You asked if you could backup system files on drive K.

    There are a few ways that I can understand this:

    I'm assuming that your system files are on drive C and you want to back them up to drive K:.
    You want to backup files from drive K to another location.

    At the same time as one of the above, you want to write data to drive L:

    If one of the above is not what you really intend, please respond with clarification.

    In any case, you can do any of these simultaneously, but there is a big limitation to be aware of.

    First, even if you are using a disk imaging program, you can write to the same volumes that you are backing up even while the image is being backed up. The way in which disk imaging programs work is like this:

    1) Briefly freeze all writes to the volume being backed up while a snapshot is created using VSS or some other snapshot provider.

    2) Allow writes to resume.

    3) Backup the static contents of the snapshot. In other words, the backup will save all data as it was the instant the snapshot was taken. Any additional writes to that volume will in no way affect the backup that is in progress.

    Now, here is the big gotcha:

    On a physical HD (not SSD) where the heads have to move across the platters, there can be a huge performance hit incurred by both reading from and writing to the same physical disk at the same time, whether or not those operations are being performed on the same logical volume or different logical volumes. This applies so long as we are talking about the same physical disk drive. The performance hit is a result of the heads having to traverse the platter to have to access data in very different locations across the platters. That jumping around between locations is extremely slow, relatively speaking.

    This applies not only to reading and writing at the same time, even just reading or writing multiple locations simultaneously is slow.

    If you ever want to prove how slow this is, try this experiment:

    1) Take a few very large files or directories. These should files or directories that take a while to copy. Select them all at the same time and copy them to another location. Time how long it takes.

    2) Logoff and back on to clear any cached data.

    3) Now, take the first file and start copying, as quick as you can, start copying the second file.

    In step 1, Windows will copy one file at a time.
    In step 3, Windows will rapidly switch between those 2 files or directories and the heads on the HD(s) will need to seek to new positions frequently. You will find that even though you are copying the same amount of data, it will take WAY longer, especially if you are dealing with directories that hold large numbers of small files.

    Bottom line is that there is no technical reason you cannot do this, but be aware of performance issues.

    Most disk imaging programs have an option to allow you to set priority. This will allow any disk operations that you perform while a backup is taking place to not be affected so drastically, but may cause the backup to take a lot longer as it continues in the background.
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  5. Posts : 2,803
    Windows 11 Pro, 22H2

    Some follow up to my above post.

    I highly simplified the process that takes place using VSS to create a snapshot, however, if you are interested in learning more about how this works, here is an article from Microsoft that goes into more detail:
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  6. Posts : 7,118
    Windows 10 Pro 64 bit

    I'm doing something similar. My desktop PC has a SSD system drive and a 2TB hard drive for user files. That 2TB drive has two partitions - a 1.5GB partition D: for user files and a 500MB partition X: for scheduled Reflect backups.

    Drive X: is used for backups of the SSD system drive. All files are also backed up to an external drive and another external drive kept separately from the PC. As far as I am aware, there is no problem using drive D: whilst files are being backed up from the system drive to X:.
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  7. Posts : 17,349
    Windows 11 Pro

    Berton said:
    Have to agree with OldNavyGuy [once was one of those] but would ask about the need for a Logical drive since only 2 partitions are involved [can have up to 4]. I'd go with 2 Primary partitions and neither one Active [not needed if not a boot drive].
    Primary Partition, Logical Partition and Extended Partition (Disk Partition Basic)
    The 4 primary partition limit is for MBR partitioned drives. @1ThursdayJC stated that their drive is 3 TB in size. If the entire 3 TB of their drive is usable, then it must be partitioned as GPT, with no limit to the number of primary partitions. If their drive is MBR partitioned (with 4 primary partition limit), then they can only use the first 2 TB of the drive. Also, you can't mark any partition as active on a GPT drive, even if wanted to.
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  8. Posts : 80
    windows 10 64 bit h20
    Thread Starter

    Well I am totally confused. So is it best to just buy another hard drive and use that as my backup drive. I think that is what I am going to do. All I want to backup is programs from drive C.
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  9. Posts : 17,349
    Windows 11 Pro

    1ThursdayJC said:
    Well I am totally confused.
    To be honest, so are we.
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  10. Posts : 80
    windows 10 64 bit h20
    Thread Starter


    Thanks for trying to help but your answer went over my head. I used to have a handle on MS-DOS back in the day.
    I used to have to low-level format and partition hard drives the old fashion way.
    But Windows is a whole different can of worms.

    All I wanted to do was to make a backup of all the programs on drive C plus my music files. Regardless of what the drive letter is. I have a Drive C which is partitioned from the factory as logical disk drives C, D, E. C is my boot drive.D. is a recovery drive and E is HP Tools
    I also have a drive F which is my DVD drive.
    I have a primary data drive J (external USB drive)
    I want to add another External USB Drive. For clarity’s sake we will call it Drive K. When formatted it has 2.72 TB of storage.
    I want to make two partitions on that physical Drive "K" One partition I wanted to make it a backup volume aka drive. I want to back up all programs from drive C, D, E plus music files. The second partition or volume would be for data storage.

    I don't know how to make what I am saying any clearer.
    Neither External USB HDD are bootable partitions!

    On a related note Do I need a image backup plus the standard incremental backup for any changes Heir Windows throws at us on a bi-weekly basis?
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