What is EFI Disk?

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Level 5

4,511 points

What is EFI Disk?

What is an EFI Disk and what is its purpose?

Why was it created?

Is it important and/or necessary?

I used Disk Utility in OS X Lion to re-partition a Seagate FreeAgent external hard drive which effectively erased all of the data that was previously stored on the device. I now use the drive for Tme Machine only. After I set up the drive I checked iStat Pro widget to view my system information and I see that there is a new disk labeled EFI Disk and it has partitioned 200 MB of storage for its use. This is new to me, the disk appeared after the re-partition of the external drive. Any insight will be appreciated.

iMac (21.5-inch Mid 2011), Mac OS X (10.7.4)

Posted on Jun 18, 2012 8:10 AM

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Answer 1

Best reply

hvaughan3

Level 1

13 points

May 4, 2017 7:33 AM in response to ds store

Is it safe to eject the EFI drives? If not, is there some way to hide them? I now have 2 EFI drives showing up on my Desktop and under the Devices list and I would rather not have to look at them.

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Answer 2

macjack

Level 10

111,168 points

Jun 18, 2012 8:24 AM in response to Malignance

When you create a OSX Extended disk,it is partitioned GUID. The first partition will always be GUID.

Sometimes the EFI designation becomes visible in either OS X or third party utilities. But it's always been there, ignore it.

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Answer 3

Jun 18, 2012 10:01 AM in response to Malignance

Malignance wrote:
...I see that there is a new disk labeled EFI Disk and it has partitioned 200 MB of storage for its use. This is new to me, the disk appeared after the re-partition of the external drive. Any insight will be appreciated.

It could be that in Disk Utility, you have "Show every partition" in the Debug menu set. The Seagate GoFlex Desk drives have a Master Boot Record as the first partition of the drive even when it's formatted for a Mac, which is probably used to communicate with the Seagate base it's plugged into. As macjack says, the EFI Disk is what the Mac communicates with and is normal.

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Answer 4

ds store

Level 7

30,725 points

Jun 18, 2012 11:36 AM in response to Malignance

Malignance wrote:

What is an EFI Disk and what is its purpose?

It's a small partition on your boot drive (or any GUID OS X extended drive) that stores software firmware and even programs to load before the operating system does.

https://en.wikipedia.org/wiki/EFI_System_partition

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