13 Replies Latest reply: Nov 1, 2009 1:31 AM by KJK555
synesthesian Level 2 Level 2 (295 points)
i buy 1tb internal drives dor backing up and also for video use. i usually format from partition and only use 1 partition and was wondering whats the difference between guid and apple partition and does one run better than the other when your on leopard or snow leopard. or does it matter?
thanks

macpro, Mac OS X (10.6.1)
  • V.K. Level 9 Level 9 (56,130 points)
    what backup software are you using? you should use GUID partition scheme if you are doing time machine or bootable backups. generally, GUID is the newer partition scheme with more capabilities than APM and MBR and I would use it in any case.
  • donv (The Ghost) Level 5 Level 5 (4,600 points)
    Sno requires GUID. My recollection is that Leo also does. There is no reason not to format Mac extended (journaled), although journaling can be turned on later.
  • K T Level 7 Level 7 (23,700 points)
    Intel requires GUID...been that way for a time now...

    Snow Leopard requires Intel. This is new.
  • synesthesian Level 2 Level 2 (295 points)
    well they are used for different purposes... i have a 8 core and 4 internal drives are guid. but i buy internal 1tb drives for either backing up audio and video, or i put drives in rocstor enclosures for video footage. they are all apple partioned. they work but if they are partioned guid and put in rocstor encasing would they run better/ faster? i use super duper and time machine for backing up.
    also when you say intel requires guid, thats for if its used internally and not in a enclosure right?
    thanks
  • KJK555 Level 4 Level 4 (2,895 points)
    I like APM better than GUID. Unless you install an OS on it using the install DVD, APM works fine.
    Time Machine could care less, and you can still boot clones made with Carbon Copy Cloner.

    Kj ♘
  • V.K. Level 9 Level 9 (56,130 points)
    synesthesian wrote:
    well they are used for different purposes... i have a 8 core and 4 internal drives are guid. but i buy internal 1tb drives for either backing up audio and video, or i put drives in rocstor enclosures for video footage. they are all apple partioned. they work but if they are partioned guid and put in rocstor encasing would they run better/ faster?

    they won't work any better or faster with GUID. But GUID is required fr installing OS on an intel mac so use GUID for superduper backups. also, according to apple, TM backups of an intel mac should be on a GUID partitioned drive too. just partition new drives GUID. you'll have fewer potential headaches in the future.

    i use super duper and time machine for backing up.
    also when you say intel requires guid, thats for if its used internally and not in a enclosure right?
    thanks
  • Allan Eckert Level 8 Level 8 (46,520 points)
    Hi KJ;

    Is this just a personal prejudice or do you know of a technical reason for your preference?

    So far everything I have read on GUID says that it the superior method to format a disk.

    Allan
    tiger
  • synesthesian Level 2 Level 2 (295 points)
    would it be wise for me to reformat my external drives 1 tb drives in rocstor enclosures that are used mostly for video and audio to guid and copy information back on to it with new format. thinking that these drives are going to worked hard doing audio and video editing for awhile and will work better with future operating systems as mac updates them? or if just leave them the way they are? also i have everything journaled.
    thanks and appreciate all your help...
  • KJK555 Level 4 Level 4 (2,895 points)
    If you are only using HFS+ (Mac os extended format) file system, then the GPT is not needed.
    The only technical weakness of using APM format that I am aware of is sometimes some disk
    controllers have a hard time reading the last few MB of data at the end of a hard drive, since
    APM formats a drive all the way to the end of a drive, that can be a problem. That problem is
    rapidly disappearing though, thanks to advances in disk controller technology. There is, of
    course, a simple cure: Leave a tiny amount (20 MB or so) free space at the end the drive, then
    the problem magically goes away.

    The above problem can still exist on GPT drives that don't have a windows partition at the end of
    the drive. Simply put, the EFI partition at the beginning of the drive does nothing to enhance
    the drive either technically or feature wise if all you are using is HFS+, it is just taking up space
    (200MB). The only difference between a GPT drive and an APM drive with a single HFS+ partition
    is the 200MB EFI partition at the beginning of the drive, so where exactly does the technical
    superiority come into play? If you take a GPT partitioned drive with a single HFS+ volume and
    remove the EFI partition, then write a few bytes of code at the beginning of the drive, Viola!,
    you now have an APM drive with 200MB of free space at the beginning of the drive.

    Since I own iPartition, I do exactly as as described above (for HFS+ only drives). I create a GPT
    formatted drive with Disk Utility, then using iPartition I change the partition scheme to APM.
    This removes the EFI partition at the beginning of the drive, but leaves the 200MB free space.
    Then, using iPartition, I shrink the partition ever so slightly, leaving a small amount of free
    space at the end of the drive. The beauty of this is that later, if I need to, I can use iPartition
    to quickly change the scheme back to GPT restoring the EFI partition back to the free space
    I reserved at the beginning of the drive.

    So, I hate to break your heart, but basically GPT (in Apple's case), is just a wrapper around APM
    used simply as a firmware interface to boot Bios based Operating Systems.

    So why do I prefer APM? Because simple is better, there is less to go wrong with APM as EFI
    partitions (which are part of GPT) are known to go corrupt and cause problems. It's just one
    thing less to worry about.

    Kj ♘
  • Allan Eckert Level 8 Level 8 (46,520 points)
    Hi KJ;

    Thank you.

    Allan
    tiger
  • KJK555 Level 4 Level 4 (2,895 points)
    "would it be wise for me to reformat my external drives?"

    No, GPT is not a new OS format, Apple still uses the same HFS+ (hierarchal file system) format
    on Snow Leopard with GPT drives. GPT is a firmware interface wrapper for supporting file
    systems *other than* HFS+ (Mac OS Extended), such as MS Dos (fat32 and NTFS) file systems,
    that allows those non Apple native file systems to peacefully co-exist on a drive that contains
    HFS+ (Mac OS Extended) volumes. APM is a format that I am sure will be supported for quite
    sometime to come.

    Should you ever need to convert APM to GPT, there is a program that can do it on fly without
    reformatting your drives. It is called iPartition.
    http://www.coriolis-systems.com/iPartition.php

    The only time though, that you would ever need to do that, is if you needed to install an MS DOS
    volume on the same drive where you have Mac OS extended volume(s) already installed.

    Kj ♘
  • V.K. Level 9 Level 9 (56,130 points)
    KJK555 wrote:
    "would it be wise for me to reformat my external drives?"

    No, GPT is not a new OS format, Apple still uses the same HFS+ (hierarchal file system) format
    on Snow Leopard with GPT drives. GPT is a firmware interface wrapper for supporting file
    systems *other than* HFS+ (Mac OS Extended), such as MS Dos (fat32 and NTFS) file systems,
    that allows those non Apple native file systems to peacefully co-exist on a drive that contains
    HFS+ (Mac OS Extended) volumes. APM is a format that I am sure will be supported for quite
    sometime to come.

    Should you ever need to convert APM to GPT, there is a program that can do it on fly without
    reformatting your drives. It is called iPartition.
    http://www.coriolis-systems.com/iPartition.php

    ipartition is not free.

    The only time though, that you would ever need to do that, is if you needed to install an MS DOS
    volume on the same drive where you have Mac OS extended volume(s) already installed.

    that's not the only situation where one might need GUID. the OP mentions using superduper to make a clone. if one ever wants to start using the clone as the main drive it should be GUID if you ever want to upgrade it.
    and Time machine on itel macs wants GUID partition according to apple
    http://support.apple.com/kb/TS1550?viewlocale=en_US

    what is your reason for recommending APM over GUID? this might only create extra headaches for the OP in the future. what exactly is the benefit of APM over GUID?
  • KJK555 Level 4 Level 4 (2,895 points)
    +"ipartition is not free."+

    Neither is Disk Warrior, Super Duper! and scores of other third party programs that get
    recommended daily on this forum. I consider iPartition a tool at least as valuable as Disk Warrior
    and it is cheaper, although it does not do the same thing as disk warrior, it can "save your
    bacon" when installing boot camp, fixing disk images, resizing partitions and rebuilding GPT
    partition tables, something that Disk Utility either cannot do, or many times fails to do or
    in many cases, completely hoses the drive while trying to do. It truly can save data and time
    just as efficiently as Disk Warrior. Question is: How much is your time worth? If someone were
    managing multiple terabyte drives, such as the OP, such a program might be worth taking
    a look at.

    Any time you are fooling with terabytes of information, lots of time is usually involved, unless
    you are using a high dollar RAID setup. Recommending the OP to change to GUID scheme
    using the "backup, destroy, reformat and restore" routine is insanity, especially in the light
    of the fact that it is totally not necessary. I would never recommend such a thing and I am not
    saying you did either, but if everyone falsely convinces the OP that APM is obsolete and will
    not work in Snow Leopard, then he/she may be inclined to invest weeks worth of hours moving
    terabytes of data around for nothing, getting little in return except shorter hard drive life,
    possible data loss and lots of added stress and loss of productivity. Unless you are building
    a bootable drive using the install DVD or a drive with an additional MS DOS volume, APM will
    do fine as a medium for storing data. One of the beauties of OS X is its flexibility. If a person
    is simply storing data and sharing it among both Macs and PC's, OS X will gladly accept MS DOS
    formatted media and with cheap third party help will also write to Windows NTFS format reliably.

    OS X (Snowie) clones (made with CCC anyway) will still boot from APM. Super Duper clones I
    assume will too, unless Super Duper refuses to create a intel clone on an APM drive. If that is
    the case, then it would be a Super Duper limitation, not an OS X limitation. I don't own
    Super Duper, so I am not aware of its limitations or capabilities. I do know that Carbon Copy
    Cloner and Chronosync and even Disk Utility, can produce bootable intel clones on APM drives.

    +"Time machine on intel macs wants GUID partition according to apple"+

    Doesn't say it won't work. I know for a fact TM works fine on APM. Those instructions appear
    to be generic instructions, but should you need GPT for adding a MS Dos volume on the TM disk,
    Then GPT will be required.

    So in a nutshell, GPT is required when:
    1. Installing OS X from the Apple install DVD
    2. Installing a third party bootable OS such as Windows or Linux, which when booted on a Mac is
    dependent on Bios Based boot support provided by Apple's firmware interface with GPT.
    note: Apple does not need or call upon the firmware interface with GPT feature(s) to boot OS X.

    APM is optional when:
    1. GPT features are not required.
    2. No volumes used as main boot volumes
    3. MBR (Master Boot Record) Bios based boot support not needed.
    note: Even though Disk Utility doesn't support it, good, useable volumes containing
    MS DOS (fat32, ntfs, etc.) and other non Apple file system formats can be created in free space
    areas of APM disks. Similarily, other non Apple file system formats can be created in free space
    areas of GPT disks as well (ext2, ext3, etc.). The reality is, there is a lot of untapped potential that
    exists outside of Disk Utility's limited framework. Yes, third party utilities are needed for that,
    such as those included with many Linux distributions and utilities such as iPartition. The point is:
    dare to think outside the box a little bit. Snow Leopard is obviously the most advanced OS on
    the planet. One of the things that make it so powerful is the flexibility it allows a user to get the
    job done.

    OS X allows you to save and use data in more different formats than any other OS I know of.
    You can save data in UDF, Joliet (iso), Disk Images (compressed, uncompressed, encrypted,
    unencrypted, etc.), Network Storage Solutions, HFS, HFS+, FAT12, FAT16 and Fat32. With a little
    third party software help OS X can also write to NTFS and read/write to EXT2 file systems and
    Blu Ray Disc file systems.

    If the APM format is so doggone useless, why did Apple even include it in Snow Leopard?
    I say: All file formats have built in limitations, including GPT. Know those limitations, strengths
    and weaknesses and use accordingly.

    GPT technically superior? Ha! Just dig through the forums
    and see which format (GPT or APM) users are having the most trouble with.

    Most importantly though, select a file format that is reliable and works appropriately for you
    and your data management needs within its built in design limits.

    Kj ♘