WD Elements partition map EFI problem

Hi All,
I am trying to format a 3TB WD Elements (USB 2) external HD, GUID, 1 Partition Mac Extended Journaled. The formatting goes ok.
If I click on the "3TB WD Ext HDD 1021 Media" on the left in Disk Utility and hit "verify disk", I get the following error message:
"the partition map needs to be repaired because there's a problem with the EFI system partition's file system"
A 'repair disk' goes through without hitch, but if I hit 'verify disk' again, I get the same error.
I wonder if I can just disregard this or if I will encounter problems somewhere down the line.
Thank you very much for your help.
(Verify of the actual partition does not yield any problems)

I just bought a Seagate 3TB USB Expansion External HD and have exactly the same problem when verifying the disk.
"The partition map needs to be repaired because there’s a problem with the EFI system partition’s file system.”
It repairs ‘ok’ but get the same error message when verifying again.
As this thread has been running for 4 months or so and its still a problem!.... Has anyone had problems using their ‘drives’ while ignoring the error message?
I feel very uneasy trusting the drive as a reliable backup and I'm surprised that Apple hasn't sorted this potentially serious issue out with a 'fix'.... Most especially as it appears to be a fault with 'Lion' rather than the various brands of 3TB external drives?

Similar Messages

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    Have you tried to run the verify/repair permissions and verify/repair disk through the recovery disk? If that didn't work then I would reinstall the OS after backing up. If that still doesn't work I would take it in.

  • Problems were encountered during repair of the partition map.

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              MacBook Pro (15-inch, Early 2011)
              MacBook Pro - model: MacBookPro8,2
              1 2 GHz Intel Core i7 CPU: 4 cores
              8 GB RAM
    Video Information:
              Intel HD Graphics 3000 - VRAM: 512 MB
              AMD Radeon HD 6490M - VRAM: 256 MB
    Audio Plug-ins:
              BluetoothAudioPlugIn: Version: 1.0
              AirPlay: Version: 1.9
              AppleAVBAudio: Version: 2.0.0
              iSightAudio: Version: 7.7.3
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                        EFI (disk0s1) <not mounted>: 209.7 MB
                        Untitled (disk0s2) /: 499.12 GB (418.57 GB free)
                        Recovery HD (disk0s3) <not mounted>: 650 MB
                        eDrive (disk0s4) /Volumes/eDrive: 12 GB (4.65 GB free)
              HL-DT-ST DVDRW  GS31N 
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              MICRONET FANTOM DRIVE     1 TB
                        EFI (disk1s1) <not mounted>: 209.7 MB
                        Fantom (disk1s2) /Volumes/Fantom: 999.86 GB (941.3 GB free)
              Apple Computer, Inc. IR Receiver
              Apple Inc. FaceTime HD Camera (Built-in)
              Apple Inc. Apple Internal Keyboard / Trackpad
              Apple Inc. BRCM2070 Hub
                        Apple Inc. Bluetooth USB Host Controller
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              [loaded] com.adobe.fpsaud.plist
              [loaded] com.raynersw.nshctldo.plist
              [loaded] org.cindori.AuthHelper.plist
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    User Launch Agents:
    User Login Items:
              iTunesHelper
              Dropbox
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              Flash Player
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              Default Browser.plugin
              Flash Player.plugin
              FlashPlayer-10.6.plugin
              QuickTime Plugin.plugin
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                   2%          EtreCheck
                   2%          backupd
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                   0%          coreservicesd
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              131 MB             Safari
              115 MB             com.apple.IconServicesAgent
              74 MB              Dropbox
              66 MB              WindowServer
              56 MB              com.apple.WebKit.WebContent
              49 MB              TechTool Pro 7
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              41 MB              App Store
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              1.84 GB            Active RAM
              370 MB             Inactive RAM
              1.13 GB            Wired RAM
              415 MB             Page-ins
              0 B                Page-outs
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    this is the list it gives, hope it helps
    Verifying and repairing partition map for “ST9160314ASG Media”
    Checking prerequisites
    Checking the partition list
    Checking for an EFI system partition
    Checking the EFI system partition’s size
    Checking the EFI system partition’s file system
    Checking all HFS data partition loader spaces
    Reviewing boot support loaders
    Checking Core Storage Physical Volume partitions
    Checking storage system
    Problems were encountered during repair of the partition map
    Error: Storage system verify or repair failed.

  • What does problems were found with the partition map mean

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  • External Hard Disc won't mount - Partition Map error.  Can't repair with Disk Utility

    Happy New Year all and thanks in advance for any support/advise.
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    mount
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    Full Results pasted below:
    diskutil list...
    Ethan-Smiths-iMac:~ Ethan$ diskutil list
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       0:      GUID_partition_scheme                        *1.0 TB     disk0
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       3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
    /dev/disk1
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       0:      GUID_partition_scheme                        *500.1 GB   disk1
       1:         Microsoft Reserved                         134.2 MB   disk1s1
    diskutil cs list...
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    No CoreStorage logical volume groups found
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    devfs on /dev (devfs, local, nobrowse)
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       Device Node:              /dev/disk1
       Part of Whole:            disk1
       Device / Media Name:      ST950032 5AS Media
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       Mounted:                  Not applicable (no file system)
       File System:              None
       Content (IOContent):      GUID_partition_scheme
       OS Can Be Installed:      No
       Media Type:               Generic
       Protocol:                 USB
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       Total Size:               500.1 GB (500107862016 Bytes) (exactly 976773168 512-Byte-Units)
       Volume Free Space:        Not applicable (no file system)
       Device Block Size:        512 Bytes
       Read-Only Media:          No
       Read-Only Volume:         Not applicable (no file system)
       Ejectable:                Yes
       Whole:                    Yes
       Internal:                 No
       OS 9 Drivers:             No
       Low Level Format:         Not supported

    Select the disk1s1 volume under the main drive entry, then click on the Mount icon in the Disk Utility toolbar if it goes active and see if a volume then mounts on your Desktop. If it does not, then you need to reformat the drive. And, you cannot access the volume in order to copy your data somewhere else. If you are willing to spend money on the problem, then you can always try using a software recovery utility:
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    If you stop using the drive it's possible to recover deleted files that have not been overwritten by using recovery software such as MAC Data Recovery, Data Rescue II, File Salvage or TechTool Pro.  Each of the preceding come on bootable CDs to enable usage without risk of writing more data to the hard drive.  Two free alternatives are Disk Drill and TestDisk.  Look for them and demos at MacUpdate or CNET Downloads. Recovery software usually provide trial versions that enable you to determine if the software would help before actually paying for it. Beyond this or if the drive has completely failed, then you would need to send the drive to a recovery service which is very expensive.
    The longer the hard drive remains in use and data are written to it, the greater the risk your deleted files will be overwritten.
    Also visit The XLab FAQs and read the FAQ on Data Recovery.

  • How can I reset my macs partition map?

    I have an MBP mid 2012 with 750GB HD (the higher model, with i7 2.9GHz and 8 gigs of ram) which I am possibly passing on to someone. I have the latest version of Mavericks, triple booted to include Windows 8.1 and Linux Ubuntu.
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           B. Clone to an external drive using using Carbon Copy Cloner.
              1. Open Carbon Copy Cloner.
              2. Select the Source volume from the Select a source drop down menu on the left side.
              3. Select the Destination volume from the Select a destination drop down menu on the right
                  side.
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              1. De-authorize the computer in iTunes! De-authorize both iTunes and Audible accounts.
              2, Remove any Open Firmware passwords or Firmware passwords.
              3. Turn the brightness full up and volume nearly so.
              4. Turn off File Vault, if enabled.
              5. Use Boot Camp Assistant to remove a Windows partition, if there be one.
              6. Disable iCloud, if enabled: See.What to do with iCloud before selling your computer
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              1. Insert the original OS X install CD/DVD that came with your computer.
              2. Restart the computer while holding down the C key to boot from the CD/DVD.
              3. Select Disk Utility from the Utilities menu; repartition and reformat the internal hard drive.
                  Optionally, click on the Security button and set the Zero Data option to one-pass.
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              5. Upon completion DO NOT restart the computer.
              6. Shutdown the computer.
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    So this will completely overwrite any of the steps in this process?
    sudo gdisk /dev/disk0
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    r <enter>        go to the recovery & transformation menu
    h <enter>        create a new hybrid MBR
    5 <enter>        add partion 5 to the MBR
    <enter>          accept the default MBR hex code of 07
    y <enter>        set the bootable flag
    n <enter>        do not protect more partitions
    o < enter>       print (display) the MBR
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    w <enter>     write partition table to disk
    reboot. hold down option - you should be able to boot into either Mac HD, Recovery HD, or Windows.
    I just tested this same five partition GPT and 2 partition MBR on a working system and the instructions above worked.
    Note, so long as CSM-BIOS and thus MBR are required for Boot Camp instead of EFI booting Windows, we're stuck with flaky MBR problems, as well as the 2TB disk limitation for Windows boot disks.
    If so, problem solved, thanks!

  • Unable to repair disk (Partition map) Please HELP !

    Hi,
    I have the weirdest problem with my 15" retina macbook pro.
    Earlier today, OS X automatically rebooted after some kind of bug. I was then unable to start the computer, wether it was through recovery or as usual.
    Started in Safe mode, Backed up with time machine, and restored system.
    I'm now able to boot as usual but when I launch Disk Utility, I detects an error. Please find DU log at end of this message.
    When I click Repair Disk, I continuously get the same error message (this disk needs to be repaired).
    Any ideas how I can get this error fixed ?
    Thanks so much !
    2015-02-14 19:10:03 +0100: Verifying and repairing partition map for “APPLE SSD SM1024F Media”
    2015-02-14 19:10:03 +0100: Starting repair tool:
    2015-02-14 19:10:03 +0100: Checking prerequisites
    2015-02-14 19:10:03 +0100: Checking the partition list
    2015-02-14 19:10:03 +0100: Adjusting partition map to fit whole disk as required
    2015-02-14 19:10:03 +0100: Checking for an EFI system partition
    2015-02-14 19:10:03 +0100: Checking the EFI system partition’s size
    2015-02-14 19:10:03 +0100: Checking the EFI system partition’s file system
    2015-02-14 19:10:03 +0100: Checking all HFS data partition loader spaces
    2015-02-14 19:10:03 +0100: Checking booter partitions
    2015-02-14 19:10:03 +0100: Checking booter partition disk0s3
    2015-02-14 19:10:03 +0100: Repairing file system.
    2015-02-14 19:10:03 +0100: Checking Journaled HFS Plus volume.
    2015-02-14 19:10:03 +0100: Invalid number of allocation blocks
    2015-02-14 19:10:03 +0100: The volume   could not be verified completely.
    2015-02-14 19:10:03 +0100: File system check exit code is 8.
    2015-02-14 19:10:03 +0100: Updating boot support partitions for the volume as required.
    2015-02-14 19:10:03 +0100: Reviewing boot support loaders
    2015-02-14 19:10:03 +0100: Checking Core Storage Physical Volume partitions
    2015-02-14 19:10:04 +0100: Updating Windows boot.ini files as required
    2015-02-14 19:10:04 +0100: Problems were encountered during repair of the partition map
    2015-02-14 19:10:04 +0100: Error: This disk needs to be repaired. Click Repair Disk.

    If you have a backup (for both OS's: OS X and Windows) you might try with booting to single user mode and use fsck tool: Resolve startup issues and perform disk maintenance with Disk Utility and fsck - Apple Support
    But if that would be my own mac i would probably create myself a Recovery USB Disk or Bootable OS Yosemite Installer Disk and repartition my Hard Drive and then reinstall OS X and restore data to it. If Disk Utility is reporting an issue with Partition Map Scheme i would be a bit anxious about my data stored on this drive...
    Mac Basics: Time Machine backs up your Mac - Apple Support
    OS X: About Recovery Disk Assistant - Apple Support
    Create a bootable installer for OS X Mavericks or Yosemite - Apple Support
    How to move data to your new Mac using Mountain Lion and earlier - Apple Support also Yosemite

  • Startup disk partition map repair difficulties

    Disk Utility is reporting that "The partition map needs to be repaired because there's a problem with the EFI system partition's file system." However, after booting into the Recovery HD and attempting to repair this, I keep getting the error, "Live file system repair is not supported." And yet I can verify that I am definitely not booting from the startup disk so I don't know why or how this is happening. Any ideas on next steps short of backing up, reformatting and wiping the drive?
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    Hi Richard,
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    OS X: About Recovery Disk Assistant
    Regards,
    - Brenden

  • Partition map needs to be repaired - what next?

    My iMac Intel  ( running Maverick ) has for some time problems starting up - takes for ever and works very slow. When I started from the start up manager to use disk utility I've received following messages.
    Live file system repair is not supported
    The partition map needs to be repaired because there's a problem with EFI system partition's file system.
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    Have you tried to run the verify/repair permissions and verify/repair disk through the recovery disk? If that didn't work then I would reinstall the OS after backing up. If that still doesn't work I would take it in.

  • Help Installing Leopard and issues with partition maps.

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    Hi-
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  • Windows Vista won't start or install - firmware or EFI problem?

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    open terminal, run the following command:
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    (press return, enter admin password, press return again)
    output should look something like this:
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    Password:
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    start size index contents
    0 1 MBR
    1 1 Pri GPT header
    2 32 Pri GPT table
    34 6
    40 409600 1 GPT part - "EFI System Partition"
    409640 316879664 2 GPT part - "RAPTOR"
    317289304 262144
    317551448 200889128 3 GPT part - "RAPTOR2"
    518440576 262144
    518702720 67287033 4 GPT part - "XP"
    585989753 82582
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    586072367 1 Sec GPT header
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    line is missing, then it is a GPT problem, which indicates
    that the MBR information is missing or more likely corrupt.
    also the second and third lines will read:
    start size index contents
    0 1 PMBR
    instead of:
    start size index contents
    0 1 MBR
    If the MBR info in the GPT partition is corrupt or missing,
    then (obviously) Windows won't be bootable.
    The only tool reliably capable (that I know of) of repairing (rebuilding) the GPT/EFI
    without wiping off all partitions and repartitioning the drive
    is iPartition:
    http://www.coriolis-systems.com/iPartition.php
    The command line program "gpt" is incomplete, so use
    it at your own risk:
    BUGS
    The development of the gpt utility is still work in progress. Many necessary features
    are missing or partially implemented. In practice this means that the manual page,
    supposed to describe these features, is farther removed from being complete or useful.
    As such, missing functionality is not even documented as missing. However, it is believed
    that the currently present functionality is reliable and stable enough that this tool can be used
    without bullet-proof footware if one thinks one does not make mistakes.
    http://17.254.2.129/library/mac/#documentation/Darwin/Reference/ManPages/man8/gp t.8.html
    Kj ♘

  • Seagate external drive: Partition map check failed because no slices were found

    I have a 3TB Seagate Expansion external backup drive connected to my Retina Macbook Pro via USB. The disk will not eject from a regular Finder window - it will only eject from Disk Utility. Backups seem to otherwise be running fine. I tried to verify/repair the disk in Disk Utility, and I got the following error: "Partition map check failed because no slices were found." I am able to verify/repair the partition without any problem, and no errors are found.
    I'm concerned about relying on a backup drive that may be heading south. Here is the output from diskutil info:
    diskutil info disk3
       Device Identifier:        disk3
       Device Node:              /dev/disk3
       Part of Whole:            disk3
       Device / Media Name:      Seagate Expansion Desk Media
       Volume Name:              Not applicable (no file system)
       Mounted:                  Not applicable (no file system)
       File System:              None
       Content (IOContent):      GUID_partition_scheme
       OS Can Be Installed:      No
       Media Type:               Generic
       Protocol:                 USB
       SMART Status:             Not Supported
       Total Size:               3.0 TB (3000592977920 Bytes) (exactly 5860533160 512-Byte-Units)
       Volume Free Space:        Not applicable (no file system)
       Device Block Size:        4096 Bytes
       Read-Only Media:          No
       Read-Only Volume:         Not applicable (no file system)
       Ejectable:                Yes
       Whole:                    Yes
       Internal:                 No
       OS 9 Drivers:             No
       Low Level Format:         Not supported

    @ Allan Eckert: Unfortunately, reformatting is out of the question, I have 5 years of work on this!
    @ Loner T: Yes, the firmware did successfully upgrade after router reboot and a bit of troubleshoot.
    Thanks for the quick replies. Keep 'em coming!

  • Disk Utility - Partition map needs repair because a data partition needs loader space.

    I just finished setting up both my OSX and Windows installs from scratch after fitting an SSD, which in-turn was right before my logic board died and Apple replaced it, now it looks like I have some sort of hard drive issue brewing.
    This was my plan for the SSD, and how it currently displays in Disk Utility although that wasn't the case earlier:
    And in Terminal:
    My intention was to have two boot partitions for each OS, 'Macintosh HD' and 'Win 7 Pro' and a third shared data partition 'Projects' on the SSD, which I made in Drive Genius after installing Boot Camp. I don't want Macintosh HD accessible from Windows because I'll be using Paragon HFS+ or MacDrive to give write access and don't want OSs stomping on other OSs turf, hence needing three partitions. Everything looked fine until I just checked Disk Management under windows and realised it couldn't see the Projects volume. Even though it's fine in OS X, it was just marked black/unallocated space.
    So I booted back into OSX, all my files look fine so I ran Disk Utility and the Partition tab looked really odd - unfortunately I didn't get a screenshot. All volumes reported their size correctly but visually, Macintosh HD took up most of the drive. I could see 'Windows 7 Pro' under this, but the Partition Layout section had a scrollbar, which if I scrolled down showed 'Projects' squished into a tiny gap at the bottom. I ran a Verify, which reported no problems, and at some time since the Partition Layout has reverted to how it should look (as in the screenshot above), with 'Projects' book-ended by "Macintosh HD' and 'Windows 7 Pro'.
    Now when I run a Verify on Macintosh HD or Projects volumes, it says there's no problem, but if I run one on the drive, I get this message:
    Volume Macintosh HD on disk0s2 has 0 bytes of trailing loader space and it needs 134217728 bytes
    Problems were found with the partition map which might prevent booting
    Error: Partition map needs repair because a data partition needs loader space.
    I've only managed to find one other mention of this error here, but the fix is not relevant to me because I don't have Sophos installed. I've tried Single User/Safe Mode but it just boots into normal mode, so I can't do a fsck -fy.
    ** /dev/rdisk0s2 (NO WRITE)
    Can't open /dev/rdisk0s2: Permission denied
    That value in bytes is exactly 128mb, so I suspect the problem lies with one of the invisible partitions that show up in iPartition and Disk Management under Windows, but not in Disk Utility. I have backups and I suspect the root of the problem is partitioning in iPartition after installing Boot Camp, but I've never had issues with this approach in the past so I'm wary of just giving up and reinstalling Windows again will be massive hassle because I no longer have a SuperDrive and last time it refused to install from USB.
    Anyone have any idea what's going on? It seems like the sort of issue Disk Utility should just handle, at least in Recovery mode, but it's not playing ball. It also doesn't seem like a massive problem since my files all look fine and performance is OK, so I'm reluctant to do anything major.
    I'll update with a shot of the drive in Disk Management from Windows in a few minutes, in case that sheds light on anything. Thanks!

    Similar issue here. I manually partitioned my hard disk for triple boot (using Gparted on Linux), then everything was just fine until I ran bootcamp, to do something as simple as create a boot USB.
    I get the same error as a result and have to work my way into booting, by resorting first to a Linux live USB, then restarting from the live USB, to finally reach my rEFInd boot manager, or whichever boot manager should be initialized at startup.
    I suppose that the cause in my case is that some operation "scratched" the protective MBR. See this:
    http://www.mactech.com/articles/mactech/Vol.23/23.03/APMtoGPT/index.html
    I am hoping to fix it using an external Yosemite installation media: see this guide -
    http://www.macworld.com/article/2367748/how-to-make-a-bootable-os-x-10-10-yosemi te-install-drive.html
    And as a last resort to reinstall.
    I'll admit I am negatively surprised. I need this computer for professional reasons, and for the sake of "preserving the integrity of OSX", measures defined by Apple instead tend to make partitions far easier to damage. And this problem seems to affect a number of users.
    As for what I have to go through to fix it: a 5GB download, during which I have to register my credit card to the Apple Store. "Pay first, get your free software next."
    IF Disk Utility can fix it, from the external media, then fair enough. The hassle is unpleasant but it files as "a choice".
    Otherwise you can file it safely under software design calamity.

  • Install error : disk cannot be used to start up your computer [or] MediaKit reports partition (Map) too small

    Greetings,
    I am aware that this problem has been discussed, but in long and vague discussions that I had to sift deeply to find an answer. Therefore I am posting a clear message, as this problem can be very troublesome for someone who just received a Mac OS installation disk and cannot install it.
    Situation : you cannot install/update your new system because the installer does not consider your volume.
    Error message : this disk cannot be used to start up your computer.
    Version française : Ce disque ne peut pas être configuré pour démarrer votre ordinateur.
    Also discussed below error: "MediaKit reports partition (Map) too small"
    Note : although this occurred with a Snow Leopard (10.6) install DVD, it can alo occur with Lion (10.7) according to discussions on Apple web site.
    IF YOUR CONDITIONS ARE AS FOLLOWS :
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    - Your main Mac partition scheme is in GUID as it should be (check with Disk Utility). That partition contains a Mac system that can start-up.
    - Your volume format is: Mac OS Extended (journaled) [the format should not be Case Sensitive.]
    - You have the hardware requirements to install Mac OS 10.6 (Intel processor; internal or external DVD drive or a linked DVD drive; 1 GB of RAM; a screen controlled by your computer graphics card; at least 5 GB space on the hard disk or 7 GB if you install all components).
    - Using Disk Utility, you of course tried the disk Repair Tool and the Repair Permissions tool.
    - Your hard disk does not have a file called Backups.backupdb (if it does, this means Time Machine has once used this hard disk for its back-ups). Anyhow, if it were the case, the installation would give a different error message (with the word TimeMachine). This file may block the installation: Apple Support suggest to place it in the garbage, *without* deleting it, and placing it back on the disk later. Mind you, if you do not use this hard disk as such to save your Time Machine back-ups, you can simply delete this file.
    HOW TO FIX :
    1. Boot with the 10.6 install DVD (Tip: you can either select Mac 10.6 as the boot DVD in your Start-up Preferences or simply press down c during the start-up).
    2. Above the install screen, you have a Utilities tab from where you can run Disk Utility. Select your hard disk and select the Partition tab. Resize the primary Mac partition (don't add a new one) by decreasing it by about 5 GB.
    It will look like this http://i.imgur.com/jHTbr.jpg
    ( That image shows only one partition, but the same principle applies even if you have two or more partitions on your disk.)
    Also see the official Apple how to: http://support.apple.com/kb/TS3926
    Version française: http://support.apple.com/kb/TS3926?viewlocale=fr_FR
    3. Commit the change by hitting "Apply"
    3.b. If you get the error "MediaKit reports partition (Map) too small", this is a rare error where the partition that follows (for example Bootcamp) is slightly overlapping your main Mac partition. You will need to reduce that other following partition. Once you have reduced the other partition, you will probably need to return to step 2 and 3 and try again.
    [ For example, in my case, I had resized my Bootcamp with CampTune software and it would seem that the file system ended-up somehow larger than the actual partition container. I simply asked CampTune to reduce the partition a bit (barely 2 GB) and that fixed it.]
    4. Reboot, again into the 10.6 install DVD.
    5. You can then install 10.6.
    6. Once 10.6 is installed, use the Disk Utility on the desktop (you can boot into the primary HD at this point) to resize the primary partition back to its original or maximum size.
    SOURCE (main fix): http://forums.macrumors.com/showthread.php?t=774410 [and] http://support.apple.com/kb/TS3926
    SOURCE (explaination for MediaKit error): some Apple discussion post.
    nb: in my case, it was on a MacBook Pro (late 2008).

    GasMan4932 wrote:
    When I click on the icon for this drive, the warning message below states "Mac OS X cannot be installed on 'iMac HD', because this disk cannot be used to start up your computer." Obviously that's not true, since that's where the OS is installed.
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    For some users with these partitions, the fix has been as simple as "tickling" (slightly changing) the partition size of some partition with Disk Utility, which apparently updates the GUID partition scheme table info so that the SL installer accepts it as safe to use with SL.( In this sense, the message may be trying to say the installer thinks the disk can't be used to reliably start up your computer with SL, not in general.)
    See the discussions topic Cannot install Snow Leopard over 10.5.8 for more about this.

  • Partition Map Schemes: HFS+ and FAT32 partitions with OSX and Windows

    OK so I know this question has been practically beaten to death, but I keep finding conflicting information. I am using a 2011 MacBook Pro, on which I will set up Windows through Boot Camp. I recently purchased a 750 GB WD external hard drive to use with time machine for a backup on my Mac. However, I also need to be able to use part of this for Windows files. SO.. I intend to use the HFS+ partition for the the Mac (500GB) and create a FAT 32 partition (250GB) to use for backing up windows files (using it for solely computer modeling and need to be able to transfer/share files with Mac users who use Parallels as well as copying to PC desktops). My question is what to use as the partition map scheme. I have heard that when using these two partition types, a Master Boot Record is needed (so Windows can recognize the FAT32 partition) and also that a GUID partition map is required for use with time machine, meaning windows would no longer be able to read the FAT32 partition. Is there a way to reconcile this? Either using Time Machine with HFS+ partition that is set to MBR or uisng FAT32 on Windows with a GUID partition map? Also if I were to use Parallels (with a GUID setup) instead of Boot Camp, could that be the way to save the windows files to the FAT32 Partition and avoid problems with Time Machine not working with MBR? Thanks for any expertise, as I have heard that both setups that I have mentioned both will work and both will not work. Any experience with a similar situation?

    Wow. Thanks for the extremely quick responses. Just for a few points of clarification.. I'm a complete newb at backing up strategies.
    Steve, you would recommend to not backup files from my Mac OSX and files from Windows (also on my Mac) on the same drive, correct?
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