Danielle Kamp

Q: Changing size of two partitions

Hi,

I have 3 partitions on my computer. Let's call them A, B and C with A = primary boot, B and C are just data. I wanna make partion B 50GB smaller and partition C 50GB bigger without losing any data (given that there is at least 50GB free space on B of course). I seams as if this is not possible within MacOS (you can make a partition smaller, but never bigger, you cannot redistribute the free space). There are a lot of posts on this topic, although I could not find an answer to my question, because most people ask for how to make the primary boot partition bigger which is a bit trickier. But how can you change a non-boot partition in Snow Leopard? Is it even possible without any 3rd-party software? If not what is the your most trusfull application?

MacBook Pro 17", Mac OS X (10.5), 2.0 GB RAM

Posted on Feb 1, 2011 3:08 AM

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Q: Changing size of two partitions

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  • by R C-R,Solvedanswer

    R C-R R C-R Feb 1, 2011 4:23 AM in response to Danielle Kamp
    Level 6 (17,633 points)
    Feb 1, 2011 4:23 AM in response to Danielle Kamp
    You can freely resize partitions using Apple's provided Disk Utility application but it cannot move the +start of a partition+. IOW, Disk Utility can't move the starting point of your partition C "up" into the space made available by making partition B smaller.

    There are third party utilities that in effect can do this, but they actually involve moving all the partition's files from one part of the disk to another so for safety's sake all of them strongly recommend making a backup of all the partitions on the drive beforehand. That's because changing the drive's partition scheme data & moving around so much data on it cannot be made 100% bulletproof so there is always some small but non-zero chance that the process will fail & you will be left with a drive that must be reformatted to again become useable, making all its previous data unrecoverable by normal means.

    Because of this need to back up everything (which is true whether or not you want to repartition anything), & because these utilities are relatively expensive, I think it is usually simpler & better to invest in a backup drive, clone the partition(s) that you want to move to it as needed, delete those cloned partition(s) on the original drive, create new one(s) with the sizes you want, & then clone back the original content from the backup clone(s).

    So for example, you could resize partition B smaller, clone partition C to your backup drive, delete C from the original drive, create a new partition C starting at the end point of B, & clone the backup of C back to it.
  • by Nyshimura,

    Nyshimura Nyshimura Feb 1, 2011 6:00 AM in response to Danielle Kamp
    Level 1 (0 points)
    Feb 1, 2011 6:00 AM in response to Danielle Kamp
    I recommend a hard disk case and make your profile backup and creates the partitions from scratch a pro system and the other a 50GB size that remains, after this backup to restore your profile
  • by Danielle Kamp,

    Danielle Kamp Danielle Kamp Feb 1, 2011 2:06 PM in response to R C-R
    Level 1 (15 points)
    Feb 1, 2011 2:06 PM in response to R C-R
    Hmm, ok. Thanks for the clarification. I think I will not get around buying a new HD then.
  • by Monty1945,

    Monty1945 Monty1945 Feb 1, 2011 2:53 PM in response to Danielle Kamp
    Level 3 (690 points)
    Feb 1, 2011 2:53 PM in response to Danielle Kamp
    Greetings,

    Use iPartition - It works well, and I have used it for many years. You can resize any part of your drive, including the boot drive. It's cheap, as well - http://www.coriolis-systems.com/iPartition.php

    Cheers,
    M.
    *****
  • by Pondini,

    Pondini Pondini Feb 1, 2011 3:34 PM in response to Danielle Kamp
    Level 8 (38,747 points)
    Feb 1, 2011 3:34 PM in response to Danielle Kamp
    Danielle Kamp wrote:
    Hi,

    I have 3 partitions on my computer. Let's call them A, B and C with A = primary boot, B and C are just data.


    That's rarely a good idea. OSX works best with everything in the same partition of a single drive. With the data and free space divided up, performance won't improve, and may very well be degraded.

    It guarantees longer seek times, as the drive head must move across the free space when going from one partition to another.

    If you guess wrong about the sizes, you can either waste free space on one or more partitions, or have too little, increasing fragmentation and slowing performance.

    Also, OSX's +Adaptive Hot File Clustering+ feature can't move data from the data partitions to the OSX volume if it would be more efficient there.
  • by Danielle Kamp,

    Danielle Kamp Danielle Kamp Feb 2, 2011 12:02 PM in response to Pondini
    Level 1 (15 points)
    Feb 2, 2011 12:02 PM in response to Pondini
    Hi,

    I am a graphic designer (mostly 3d rendering), so I divided my HDs up like this: A: OSX system + programs, 2: Graphic Projects, 3: Video Tutorials + Video Guides, 4: Reference Images

    All partitions (except the first) are all above 500GB, so I have no other choice than doing it this way. I use 2 big HDs with partitions. If I would use one giant HD I also would loose everything if this one breaks down (I do backups of course) but still... What you think?
  • by Pondini,

    Pondini Pondini Feb 2, 2011 12:27 PM in response to Danielle Kamp
    Level 8 (38,747 points)
    Feb 2, 2011 12:27 PM in response to Danielle Kamp
    Separare drives are very different from separate partitions on the same drive. That usually is a good idea, and usually will result in better performance.

    The reason is, each drive has it's own access arm, moving independently; different partitions on the same drive are accessed by the same one.

    You should have OSX, your apps, and user home folders on the OSX drive, usually with at least 15% to 20% free space (more is usually better). You may want to move some things that are normally in a home folder to a separate drive, such as your iPhoto and/or iTunes libraries, and video files.

    Your other drive might work well with separate partitions, unless they tend to be accessed frequently at the same time. But if you regularly use, say the Reference images in your Projects, the access arm will have more miles on it than the Space Shuttle if they're in different partitions (pardon the slight exaggeration ).

    OSX uses "Adaptive Hot File Clustering" on the OSX volume; it will actually move things that are often accessed to the fastest part of the partition, and things that are frequently accessed together to the same part of it, and adjust that as your workflow and habits change. I'm not sure if that's done on a data-only drive as well.

    If you do have stuff in those partitions that isn't used much, put it in the partitions towards the bottom of the diagram that Disk Utility presents; that's the slowest part of the disk. See #1 in [Formatting, Partitioning, Verifying, and Repairing Disks|http://web.me.com/pondini/AppleTips/DU.html] (or use the link in *User Tips* at the top of the +Using Snow Leopard+ forum) for a sample.
  • by theheds,

    theheds theheds Aug 22, 2015 6:16 AM in response to Monty1945
    Level 1 (0 points)
    Aug 22, 2015 6:16 AM in response to Monty1945

    Hi Monty,

     

    I have a 1TB external hard drive that is partitioned in 3 ways.  I need to move some storage space from partition A to partition B without having to reformat.  Will this program work for what I want to do?

     

    Thanks