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I'm experimenting with files mounted as loop devices which are tied together to a RAID 5.

When I use fdisk to create a primary partition for the array, it asks me for the first cylinder which can be in the range 1-10176. The default is 65 and I wonder why it is not 1?

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Hmmm, doing a sudo mkfs.ext3 /dev/md0p1 tells me that the partition's alignment is offset by 63488 bytes and that this may result in very poor performance. Might this be the reason for the first cylinder default? – fabb May 1 '12 at 17:12

Typically the first series of cylinders are reserved for the MBR, Master Boot Record. This is reserved so that you can have JUST boot information for the drive, and partitioning information too, in a dedicated space which Operating Systems should not typically interact with.

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I thought so too at first, but when I inspected some fdisk examples, the first cylinder default was always 1 there. Are you sure that your answer is correc? Or could it have to do with the comment I posted above at the question? – fabb May 1 '12 at 17:14
@fabb I'm not certain. – BloodyIron May 1 '12 at 17:16

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