External HD formatting questions

Discussion in 'Mac Basics and Help' started by eVolcre, Sep 20, 2008.

  1. eVolcre macrumors 68000


    Jan 7, 2003
    I have a 250GB portable external HD. Of this, I need a 100 GB bootable partition for a cloned drive and a 30 GB WINDOWS readable partition for essential files to be shared in case of a catastrophe in the field.

    If I partition 1 HFS 100GB partition for the clone, 1 120 GB HFS to store my photos and music (MAC only) and one 30 GB FAT 32 for my transferrable files, will I be able to boot off the 100 GB clone in case my HD fails? Any other options you can think of?

    Finally, does splitting an existing partition into two delete existing data? I have a 120 GB HFS partition of which I'm using about 50. Lets say I split it using disk utility into a 80 HFS, 40 FAT. Will it leave the existing HFS data as it is and add an empty FAT 40 GB slot?

    Hope this isn't too confusing.

  2. sickmacdoc macrumors 68020


    Jun 14, 2008
    New Hampshire
    You can do that easily in Disk Utility and it will work fine. The main thing to remember is that when you enter Disk Utility and select the whole drive in the left column (not a partition on the drive), you will then go to the "Partiton" tab.

    • Change the "Volume Scheme:" from "Current" to "3 Partitions"
    • Immediately go to the "Options" button at the bottom and click it
    • From the window that appears, be sure the right partition type is selected for your Mac- "GUID Partition Table" for Intel Macs or "Apple Partition Map" for PowerPC based Macs. Do not select "Master Boot Record" for PCs.
    • After that is done, drag the line between each partition to adjust the sizes of each. To check the sizes, click on each partition and the individual size will show to the right of the map.
    • Now click each partition and assign a volume name and format type to each. Use "Mac OS Extended (Journaled)" for the first two, and "MS-DOS (FAT)" for the final one. Make sure you don't exceed 11 characters for the FAT partition name BTW
    • Click Apply, review the information and click "OK" to continue.

    BTW- for several reasons that aren't important now, make sure your FAT partition is the bottom one in the list. Also, if you are on an Intel based Mac so have used the "GUID" selection, the FAT partition will be visible to Windows when hooked to a PC. I forget if Windows can see it if you needed to use "Apple Partition Map" above for a PowerPC Mac but I believe it does.

    Yes, under your situation as you have described assuming you are running in Leopard you could split that partition non-destructively. You would drag the bottom border of the partition upward in the "Partition" section of Disk Utility which would then show the remainder of the space that had been used as a grey block. Disk Utility will not let you shrink it too small to hold the current amount of data. Clicking the "+" button at the bottom would add a new partition to utilize the grey "free space". You would then select the new partition, give it a name in the "Volume Information" area and select "MS_DOS (FAT)" (as that is the name that Disk Utility uses for FAT32), then click "Apply". It will give you a summary of what is to happen (specifically noting what will or will not be erased) and if you agree to that you click OK to continue.

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