# Track/Cylinder allignment on GPT disk



## Beeblebrox (Sep 4, 2011)

I have done a considerable amount of searching and reading but cannot locate a satisfactory answer about partitioning to track boundary on GPT:
* Is track & cylinder allignment important in FreeBSD? (I assume yes or is it more important in WÄ°n/Linux)
* Is it important on GPT disks? (I assume yes or is it more an MBR thing)
* Using gpart -a  does not necessarily allign to track from what I can tell, and a script to calculate must be used (see aragon)...  Really? That hard? Parted under Linux makes it way easier than gparted if you are going to need scripts etc.

I have a headache now so I'll stop trying to figure it out.


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## jem (Sep 4, 2011)

Aligning MBR partitions to cylinder boundaries is an ancient legacy thing from the early days of MS-DOS, when the geometry reported by a disk actually reflected its internal physical layout.

It simply has no relevance in this age of Logical Block Addressing.  I don't understand why FreeBSD even warns about incorrectly aligned partitions any more.

It certainly isn't relevant for GPT partitioning.


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## aragon (Sep 4, 2011)

jem said:
			
		

> I don't understand why FreeBSD even warns about incorrectly aligned partitions any more.


I guess because there's enough legacy software and firmware to warrant it...


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## wblock@ (Sep 4, 2011)

Go back to whoever suggested that aligning to tracks was still necessary--or even possible--and ask them why.  Then ask them how to pull it off with a drive with variable geometry, where the outer tracks have more sectors.  Then ask where to get a drive that isn't variable geometry.

Sector alignment, OTOH, is a different matter.  When most new drives have 4K sectors but lie and pretend to have 512-byte sectors, it can make a big performance difference if aligned to even multiples of 4K.


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## Beeblebrox (Sep 4, 2011)

@aragon & @wblock:
But in "general" terms for ZFS on GPT disk running FreeBSD-9, you would agree that cylinder alignment is insignificant / ancient?


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## wblock@ (Sep 4, 2011)

The word I would choose is "impossible".


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## AndyUKG (Sep 5, 2011)

The only alignment issues you need to worry about are if you are using Advanced Format drives (because they lie to the OS about their sector size). But it's a totally different issue than your original question, just thought I'd chip in in case you were getting the two confused...

ta Andy.


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## Beeblebrox (Sep 5, 2011)

@ wblock: Thanks Warren, you're the man!


> Then ask where to get a drive that isn't variable geometry.


answer: Solid-state device...
This, of course, is a troll answer and has nothing to do with my original question 

Also, thanks AndyUKG for the input.


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