Subject: Re: bug#22180: Partition alignment using parted

From: Phil Susi <[email-masked]>
Date: Wed, 23 Dec 2015 12:19:43 -0500

On 12/23/2015 8:35 AM, Ankur Tank wrote:
> Hi Phillip
> 
> Thank you very much for reply, We are using am335x based (Beaglebone
> Black) custom board with eMMC(4GB). I have couple more questions
> regarding partition alignment. 1. Does partition alignment guarantee
> performance improvement ?

No; it depends entirely on the underlying storage device.  Your average
hard disk does not care at all about alignment.  Hard disks that
internally use 4k physical sectors but report 512 byte logical sectors
will see a significant performance difference between a partition that
is aligned to 4k or not.  A raid array performs much better when aligned
to a multiple of the stripe size.  The performance characteristics of
flash vary greatly.

> 2. Is it required for all the partitions to be aligned ? Because we
> are creating four raw partitions at the beginning of the eMMC which
> can't be on 1MB boundary.(because ROM code looks at on 128kb blocks
> only).

No, it is not required. And especially for a mostly read only partition,
it really doesn't matter as it is only writes that suffer from improper
alignment.

> 3. Is there any better way to get partition aligned. (I know I
> sound silly but I wanted to know if there is any better method ). 

I'm not sure what you mean.

> 4.
> parted is not allowing to use ~340 MB of size at the end of the eMMC,
> why so ? Am I missing something ? 5. I don't see verbose option for
> parted in man page, Is there any way to enable it?

I can't read your mind, so you will have to describe what you are
actually seeing.