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Question: Disadvantages of Master Boot Record?

Hi guys!

I am unsure whether to choose GUID or MBR scheme partition.

The second one is quite useful to read FAT32 partitons from Windows or other devices.. But what are the consequences for my Macs?

Thanks in advance!

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You seem focused on performance, partitioning, and on Microsoft Windows product support.


As for performance when you're looking at MBR or GPT in the context of I/O performance and external storage, any differences will be completely obliterated by the glacial speed of USB2 and by the general slowness of magnetic disk storage. Hard disks are slow. USB is even slower.


Internally, the implementation of disk partitioning adds an addition or a subtraction operation involving the target disk address and the partition offset within the context of the write and read I/O paths. A single disk I/O takes the wall-clock time equivalent of thousands of instructions or more; you're looking at rotating rust and electric motors and aerodynamics here, where the partition overhead contributes a few instructions. And there's no particular difference in what happens within the partitioning between MBR and GPT here; at its core, it's an addition or a subtraction operation within the I/O paths.


Various of the Microsoft platforms do support GPT disks. Here is a discussion from the Microsoft support database, as well as various hotfixes for some of the Microsoft platforms. Though if you're (still) using Windows XP here, then this Microsoft GPT FAQ indicates you'll have problems. Looks like MBR that far back. (Though I don't use Microsoft Windows nor Office anymore, I do support some folks that do, and they're now far less of a support problem after having upgraded their remaining Windows XP boxes to Windows 7. Windows XP was all sorts of trouble.)


As for what volume format to pick, well, pick whatever format works for the current task. Offload the bits from the disk and swap formats if the requirements change, or pick up another (cheap) disk and use one per format or transfer. These days, I usually end up swapping files around via a WiFi or gigabit network or (occasionally) via a USB flash drive or SD card or maybe (rarely) via a recorded CD or DVD, or by using a laptop. Hard disk sneaker-net? That's entirely your call...


What do I think of hybrid MBRs? I wouldn't choose to use that hybrid MBR scheme. That's dancing in an area between what BIOS or EFI expects and what an MBR or GPT provides and in an area which might or might not work in any particular OS or platform or version case. I don't really need to (seek to) spend (more) time troubleshooting OS corner cases and firmware corner cases all for a hard disk.


If you're not centrally investing low-level formats, then I'd tend to pull back here, figure out what you want and need to do, format your disks appropriately for it, and move on. Disks are cheap these days, and (if you're going to sneaker-net disks) you can get older-generation drives for extra cheap. (With the older half-terabyte or terabyte disks, if you should accidentally drop one, well, no great loss.)


But if you want to experiment with your disks or to investigate low-level formats here, well, have at...

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Apr 22, 2011 2:51 PM in response to xxcgfcbchf In response to xxcgfcbchf

The correct answer depends a whole lot on what you're doing.


If you're looking to set up a disk for use on a Mac, then the short answer is to use a GUID Partition Table (GPT) disk


If you're going to use these as Mac OS X boot disks or as local data disks, then you will want to use the GPT-partitioned disks.


If you're planning to swap the disk with a Microsoft box or another platform, then you may want to use the older MBR format disk partitioning scheme.


GPT is the native partitioning structure used for the EFI console present within Mac OS X and Mac OS X Server; it's how EFI locates and boots the system. GUID is a term used for a particular signature used (in this context) in conjunction with the GPT partitioning structure. (GUID is Globally Unique Identifier; it's a form of a signature.)


The GPT partitioning scheme is an upward-compatible scheme that evolved to get around the limits of MBR. The GPT partitioning structures actually contain a properly-formatted MBR structure. (MBR partitioning provides up to four partitions. GPT disks can offer a whole lot more than that.)


FAT12, FAT16 and FAT32 (which is technically implemented as FAT28, when last I checked) are Microsoft volume structures that can exist within GPT or MBR-partitioned disks. The Mac native volume structure HFS+ can also exist within GPT-partitioned disks.

Apr 22, 2011 2:51 PM

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Apr 22, 2011 4:27 PM in response to MrHoffman In response to MrHoffman

Hi! Thank you for helping me..


Yes, you're right. I can create a FAT32 partition within a GUID scheme, but I've heard that Windows computers cannot read it (so, waht is its utility?): they require a MBR scheme.. Is it right?


In the ovrewhelming majority of cases I would use the external HDD on my macs, but nevertheless it could happen that I had to transfer files to/from Windows... That is the only reason I'm still taking in consideration MBR. Waht shall I do to reach this aim?


Anyway, a part from the boot are there other consequences for example on performances?


The last thing.. What do you thing about an hybrid MBR? Alternatively, do you know a way to creat 2 partition schemes?

http://www.rodsbooks.com/gdisk/hybrid.html



Thank you! 😉


Apr 22, 2011 4:27 PM

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Question marked as Solved

Apr 22, 2011 6:04 PM in response to xxcgfcbchf In response to xxcgfcbchf

You seem focused on performance, partitioning, and on Microsoft Windows product support.


As for performance when you're looking at MBR or GPT in the context of I/O performance and external storage, any differences will be completely obliterated by the glacial speed of USB2 and by the general slowness of magnetic disk storage. Hard disks are slow. USB is even slower.


Internally, the implementation of disk partitioning adds an addition or a subtraction operation involving the target disk address and the partition offset within the context of the write and read I/O paths. A single disk I/O takes the wall-clock time equivalent of thousands of instructions or more; you're looking at rotating rust and electric motors and aerodynamics here, where the partition overhead contributes a few instructions. And there's no particular difference in what happens within the partitioning between MBR and GPT here; at its core, it's an addition or a subtraction operation within the I/O paths.


Various of the Microsoft platforms do support GPT disks. Here is a discussion from the Microsoft support database, as well as various hotfixes for some of the Microsoft platforms. Though if you're (still) using Windows XP here, then this Microsoft GPT FAQ indicates you'll have problems. Looks like MBR that far back. (Though I don't use Microsoft Windows nor Office anymore, I do support some folks that do, and they're now far less of a support problem after having upgraded their remaining Windows XP boxes to Windows 7. Windows XP was all sorts of trouble.)


As for what volume format to pick, well, pick whatever format works for the current task. Offload the bits from the disk and swap formats if the requirements change, or pick up another (cheap) disk and use one per format or transfer. These days, I usually end up swapping files around via a WiFi or gigabit network or (occasionally) via a USB flash drive or SD card or maybe (rarely) via a recorded CD or DVD, or by using a laptop. Hard disk sneaker-net? That's entirely your call...


What do I think of hybrid MBRs? I wouldn't choose to use that hybrid MBR scheme. That's dancing in an area between what BIOS or EFI expects and what an MBR or GPT provides and in an area which might or might not work in any particular OS or platform or version case. I don't really need to (seek to) spend (more) time troubleshooting OS corner cases and firmware corner cases all for a hard disk.


If you're not centrally investing low-level formats, then I'd tend to pull back here, figure out what you want and need to do, format your disks appropriately for it, and move on. Disks are cheap these days, and (if you're going to sneaker-net disks) you can get older-generation drives for extra cheap. (With the older half-terabyte or terabyte disks, if you should accidentally drop one, well, no great loss.)


But if you want to experiment with your disks or to investigate low-level formats here, well, have at...

Apr 22, 2011 6:04 PM

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Question: Disadvantages of Master Boot Record?