Read/write disk image vs. sparse

When I create a new disk image in DU, I am given image format options of read/write disk image, sparse disk image, and sparse bundle disk image.
I understand the difference between sparse and sparse bundle, but what's read/write?

A read/write disk image is a traditional (i.e. non-sparse) disk image.
With sparse images, you define the maximum size, but they only consume as much disk space as the content on the disk image - a 1GB sparse disk image with 50MB of data takes (about) 50MB of space on disk and can grow to 1GB.
In comparison, a 1GB read/write disk image will consume (about) 1GB on disk, regardless of how much data is on the disk - 1KB, 1MB or 1GB on the image will all consume 1GB on disk.

Similar Messages

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    More from kajz
    Sorry about the typos in my first message. I was tired after fighting the sparse image problem with Lion.
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  • Disk Image Setup on Time Capsule

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    daveb74 wrote:
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  • OS X Encrypted Disk Image Tool Buggy?

    Hi,
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    Invalid Volume Header
    Checking HFS Plus volume.
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    Creating Image “raw_data.dmg”
    Initializing...
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    Greg
    MacBook (Intel)   Mac OS X (10.4.10)  

    Is the external drive a USB drive formatted as FAT32? If it's USB and you're using it "out of the box" without having reformatted it, then it's probably FAT32.
    FAT32 filesystems can't properly hold a file larger than 2GB. I ran into this with a pocket size 12GB USB drive. Once the sparseimage file gets close to 2GB, things go haywire.
    If you don't need to share the drive with Windows machines, reformat the drive as Journaled HFS+, and the problem should go away. Otherwise, keep the sparseimage files well under 2GB.

  • Questions related to Disk Images - Image Format Options

    Can anyone tell me a more about using Disc Images? I am with a group of new Mac Users and we're focusing on Disc Images at the moment. Want to create a Keynote Presentation for the group when finished.
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    Unanswered Question:
    1) What is the difference between sparse Disk Image and sparse bundle Disk Image?
    Answered Question (if you have ad-on Informations for the answered Questions feel free to jump in):
    Question: What is sparse disk Image for?
    Answer: "Choose an image format. You can use "sparse disk image" for a disk image that only uses as much space as it needs, rather than a set amount of space. If you're not sure, use "read/write disk image" choice." (Source: How to create a password-protected (encrypted) disk image in Mac OS X 10.3 or later: http://support.apple.com/kb/HT1578)
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    Thank you both for your Infos so far. In the meantime I've created some Disk Images. What I noticed is, when I choose a small Image Size like 10 MB, then it changes from "Single Partition Map" to "No Partition Map". When I go bigger to 500 MB it changes to "Hard Disk".
    It was already helpful to read the Manual to understand the Single Partition Maps, but what I still don't understand is the difference between using "no partitions map" at all and the other options such as "Hard Disk", "CD/DVD" or "CD/DVD with ISO Data".

  • Creating FAT32 Encrypted Disk Image

    I have a 2TB WD external hard drive and am looking to have half of the space used in such a way that it is password-protected and also can be accessed by both Macs and PCs.
    I have tried the following:
    Disk Utility
    New Blank Disk Image
    Size: 1TB
    Format: MS-DOS (FAT)
    Encryption: 128-bit AES encryption
    Partitions: Single partition - Apple Partition Map
    Image Format: read/write disk image
    Received this error message:
    "Unable to create "testname.dmg." (File too large)
    ALSO:
    Disk Utility
    New Blank Disk Image
    Size: 1TB
    Format: MS-DOS (FAT)
    Encryption: 128-bit AES encryption
    Partitions: Single partition - Apple Partition Map
    Image Format: sparse disk image
    Received this error message:
    "Unable to create "testname.sparseimage." (Invalid argument)
    Thank you. Any assistance would be greatly appreciated!
    AppleCare was unable to provide a solution.

    FAT file system has partition and file size limits, which apparently you exceeded. I think the file size limit for a FAT32 file system is (2^32) - 1 byte.
    See here for more info.
    http://lmgtfy.com/?q=FATFile+SizeLimit

  • About disk images

    How do disk images work?
    When you select a size for a disk image in Disk Utility does it always take up that much space or is that just the limit?
    What's the difference between sparse and read/write encrypted disk image?
    Can either of these formats be opened in Windows, including non-encrypted ones?
    Thanks

    1. When you set a size for a disk image that is the amount of space reserved for the image file. It will take up slightly more than that on a hard drive because of the directory overhead. You can store slightly less than the reserved space also due to directory overhead.
    2. A sparse image, unlike a regular disk image, is created with an allocated maximum storage space but will occupy less space on the hard drive. The size of the image file will grow as more data are "written" to the image file. When File Vault creates an encrypted Home folder it does this be moving the Home folder to an encrypted sparseimage disc. Thus, a File Vault protected Home folder can increase in size to accommodate new files.
    3. An encrypted disk image is just that. A disk image that is encrypted and requires a password for access to its contents. A read/write disk image is one on which you can add or remove content. A read-only image is one that once you have written to it you cannot change it.
    4. Mac formatted devices (including disk images) cannot be read on PCs without special software. However, a standard disk image that is not restricted to only the Mac disk format will contain alternative filesystems that are readable on PCs.
    Open Disk Utility and select Disk Utility Help from the Help menu. Search for references to disk images for more complete information.
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  • Encrypted Disk Image Seems Full But Is Not 10.5.6

    I've created a 20 gig encrypted Read/Write disk image (not a sparse image) using Disk Utility. The image resides on an external hard drive. I back up a 900 mb file each day to the encrypted disk image. There are six such files on the encrypted disk image, but the folder shows only 526 MB of free space left. Does someone know why this is happening and how to avoid it? (It happens as well when I back up the same file to an encrypted disk on a flash drive. I delete and replace the file and this process seems to eat up space on the disk image.) Thanks.

    when you delete a file you have to empty trash while the disk image is mounted. that should free up the space on the image. I would also recommend using sparse image instead of a regular one. it will take less space on the hard drive and you can make it bigger if you have to.

  • Unable to create an encrypted disk image in Lion

    disk utility gives the error Unable to create "Volume.dmg." (error - 60008) when creating an encrypted disk image. I am using the following steps:
        1.    Open disk utility
        2.    Select the disk (internal or external) to create the image on
        3.    Select File>New>Blank Disk Image…
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        5.    Name: Volume
        6.    Size: 50GB
        7.    Format: Mac OS Extended (Journaled)
        8.    Encryption: 128-bit AES encryption
        9.    Image Format: read/write disk image
        10.    Click the Create button
        11.    Password dialog appears
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    I have previously, successfully, created encrypted disk images in Snow Leopard, and I don't know why I can't in Lion
    Does anyone have any ideas?

    Thanks for this Thomas.
    I've tried naming the image differently, but still received the error, I did however try different permutations for the password.
    The error seems to happen if I use a purely numerical password string and occurs on input of the 10th numerical character, if I start with numerical character but use an alpha before the 9th number I can continue and create a password, and I can create a password  if I start with an alpha and switch to numerals after the first alpha character, purely alphabetical passwords are fine too.
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    Thanks for your help

  • Unable to create an encrypted disk image with Disk Utility

    Hi:
    With our upgrade to Lion a few weeks ago, we're now unable to create an encrypted disk image of any type using Disk Utility any more. This problem occurs on 3 different machines, and is reproducible whether one is using an internal HD or an external FW HD. We can successfully create nonencrypted disk images.
    This is a duplicate post with all the details here: https://discussions.apple.com/message/18469359#18469359
    We haven't had any luck with a solution trying various permissions fixes as helpfully suggested by other readers in response to the error message # (-60008 error), so I'm hoping that someone else has run across a solution from the encrypted disk image perspective and that this tag line will generate some help.
    Thank you!

    Save As: 01 (on Desktop)
    Name: 01
    Size: 100 MB
    Format: Mac OS Encrypted (Journaled)
    Encryption: 256-bit AES
    Partitions: Single partition- Apple Partition Map
    Image Format: read/write disk image
    At the password window that pops up I enter: 1234567890
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    Name: 02
    Size: 100 MB
    Format: Mac OS Encypted (Journaled)
    Encryption: 256-bit AES
    Partitions: Single partition- Apple Partition Map
    Image Format: read/write disk image
    At the password window that pops up I enter: 1234567890 and when I start to enter the next "1" I get the "Unable to create "02.dmg." (error -60008)
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    Disk Utility Version 12.1.1 (353)

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