GUID vs MBR
Posted on July 15th, 2009 by Jon
My iMac recently took a dump… a real slow dump. It pissed me off because it looks like it was the HDD again. Yeah, I’ve only had it for 1.5 years and the HDD has crashed twice. The first time Mac replaced it and this time I went with a green WD 1T drive. A nice upgrade from 320G. Great, huh?
If you don’t know, an iMac has no visible screws except for the one covering the RAM, so pulling the drive is oh so much fun. I’d rather not do it again. I got the 1T drive installed, booted to my Leopard “upgrade” disk and went about tricking it into a full install as usual (tell it you want to restore from backup and then immediately cancel out). I went into the disk utility (which wouldn’t even see my old drive but xp would in an external enclosure…), and I went to format the drive. It was FAT formatted and I like my Journaled format.
After hitting the erase button (which also formats) it errored out after just a few secs. I tried again, and again, and again. No dice. I kept getting an error that the formatter was failing. This happened both on the disk and the partition. A quick search on Google revealed that larger drives won’t work if formatted as MBR, but will as GUID. If you use the disk utility, go under the partition tab, and then options, and then change it from MBR to GUID. Great. Hit apply and it freakin formats your monster sized disk. Heres why….
GUID is more flexible than MBR as a partitioning scheme because of a number of reasons. Here we go:
- MBR only supports 4 primary partitions, otherwise you have to use extended partition tables (doesn’t sound that bad)
- There is no standard that defines much of how MBR is implemented. It utilizes disc geometry to create cylinder boundries… what if it mismeasures? Oops.
- GUID Partition Table (or GPT as you’ll see MS cal it) is not constrained by container size. Neato. That means resizable without data loss (like a built in partitino magik!)
- GUID is standards based. It has a primary and backup table, and uses CRC32 for error checking. Hardcore.
- The maximum raw partition size is 18 exabytes. I need that.
- GPT can have an unlimited number of partition (which are 16 character human readible names, not 2 bytes of uselessness like MBR)
- GPT is preceeded by a protective MBR to protect against unaware programs like fdisk.
The bottom line: GUID is slick. Use it, love it. MBR is obsolete… not even MS uses it anymore.
~Jon
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4 Responses to “GUID vs MBR”
1Brad
July 16th, 2009 @ 8:39 am
Just wanted to point out that your trick of using an upgrade disc for a full install is sweet!
2Jonathan Haddad
July 16th, 2009 @ 11:18 am
Saw your post on rustyrazorblade – thanks for elaborating on the differences between MBR and GUID, as well as the link back. I’ll update my post to link to your extra info.
3Rusty Razor Blade » Blog Archive » Western Digital Drive with Leopard - “File system formatter failed.”
July 16th, 2009 @ 11:20 am
[...] here’s a few reasons why GUID owns MBR These icons link to social bookmarking sites where readers can share and discover new web [...]
4Brad
July 16th, 2009 @ 11:24 am
Thanks for the link love….
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