Re: using GPT support in BIOS boot

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Sun, Jan 09, 2011 at 10:09:18AM -0500, Greg Troxel wrote:
> I understand why 4KB alignment makes sense (larger physical disk blocks
> on disks that present 512 byte sectors), and 128KB/256KB/1MB seem
> broadly sensible, but I would appreciate understanding what bad thing
> would happen with starting the first GPT partition at:
> 
>    34 sectors/17KB    (messes up 4KB alignment, splitting reads/writes)
>    36 sectors/18KB    (ditto)
>    40 sectors/20KB    ?
>    64 sectors/32KB    ?
>   128 sectors/64KB    ?

The central idea is that the underlaying device may have a write unit
that is larger than one sector or 4KB. Both for RAID 5 and SSD this is
often the case. It will work, but it can easily trash performance.

Joerg