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I ran fdisk with these options,

fdisk -H 32 -S 32 /dev/sdc

Then I made a new label, and created an aligned first partition.

Disk /dev/sdc: 7743 MB, 7743995904 bytes
32 heads, 32 sectors/track, 14770 cylinders, total 15124992 sectors

However when I run,

fdisk -l /dev/sdc

My heads are reported at 16, like this,

Disk /dev/sdc: 7743 MB, 7743995904 bytes
16 heads, 32 sectors/track, 29541 cylinders, total 15124992 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xd84c4698

Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            8192    15124991     7558400    c  W95 FAT32 (LBA)

Why does the disk not show the 32, as I specified when creating the partitions? Is it just displaying 16, but everything is still actually as I specified?

Really just want to make sure I'm still correctly aligned.

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Can you add the output for fdisk -l /dev/sdc to your question? –  jippie Apr 30 '12 at 18:19
    
@jippie: Just updated the question with that info. –  TechZilla Apr 30 '12 at 18:32
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2 Answers

up vote 2 down vote accepted

Units = sectors of 1 * 512 = 512 bytes Your partition starts at (Start) 8192 × (Unit size) 512 = 4MiB

I don't know what your intention was, but it doesn't look too bad as it is on a 32×32-boundary too (4096).

Don't know why fdisk says 16, but it looks all right to me. Maybe check the manual page man fdisk for more details.

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That is exactly what I wanted, 4MB. I'm also confused about the 16, but as long as my partitions are still acceptable... Thanks for your help! –  TechZilla Apr 30 '12 at 19:13
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Cylinders, sectors, and heads are leftover cruft that have not actually existed on hard disks since about 1990. You should simply ignore them whenever you see them, as they are meaningless.

parted will make sure your partitions stay aligned to a 1 MiB boundary, which should be plenty of alignment for just about any device. I believe fdisk now does this as well. If you want to make sure, simply put it in sector mode and specify a starting sector that is an even multiple of the device's optimal alignment size.

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First off, while 1MB offset is perfectly fine for most situations, 1MB is not acceptable for my situation. In addition, while CHS are theoretically meaningless they still have pragmatic effects in this circumstance. I'm unable to explain why in this small comment, but here is a links which talks about SSD and alignment. ocztechnologyforum.com/forum/… –  TechZilla Apr 30 '12 at 19:21
    
I also should mention, the SSD that link talks about has an EBS of 512K,. My particular EBS is not that small, so it's not the same exact circumstance. All in all, how you set up the drive has performance and longevity consequences. Obviously if your working with a standard HD, you don't need to worry about things like an EBS or Page size. –  TechZilla Apr 30 '12 at 19:22
    
@TechZilla, CHS is still meaningless. If you need more than 1MB alignment, and the device optimal alignment is not automatically detected ( is not in your fdisk output ), then you will just need to put fdisk in sector mode and specify an aligned sector. Playing games with the bogus geometry isn't going to help. Also SSDs do not need erase block alignment. They can ( and will for wear leveling purposes ) relocate smaller writes to any free erase block. That smaller write size is usually either 512 bytes or 4KB, but certainly will be less than 1MB. –  psusi Apr 30 '12 at 19:34
    
You made an assumption I was working with an SSD, while I provided a link regarding SSDs, I only stated the generic 'NAND' in my OP. So while your correct about modern SSDs, the same EBS/Page generalization does not apply to all 'NAND' Devices. You also mentioned specifying alignment by sector... Even if the -H32 -S32 values are irrelevant, by which method did I likely use get the offset of 8192??? It should have been obvious, I already specified alignment by sectors. Finally you never actually even attempted to answer my question, I don't recall asking if specifying CHS has value. –  TechZilla May 1 '12 at 16:56
    
I also didn't ask how to create aligned partitions with parted, though you provided a response. My question was regarding my already formatted partitions. BTW it has now been answered, regardless I appreciate your time. –  TechZilla May 1 '12 at 16:59
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