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[bug-fdisk] A bit further upgrade
From: |
Toshikazu Aiyama, Ph.D. |
Subject: |
[bug-fdisk] A bit further upgrade |
Date: |
Fri, 9 Jul 2010 02:52:49 -0700 (PDT) |
Thank you for your recent upgrade to start the first usable partition from
sector 2048. I do not know how you got this magic number, but Windows use it,
and it also is the suggestion by GPT developer: Rod Smith.
The following suggestion is based on util-linux-ng 2.17.2
Main reason for reserving 2047 sectors at the start is GPT conscious: PMBR &
Primary Partition Table(PPT), I believe. If you're GPT conscious, why not to
be conscious about Backup Partition Table(BPT).
Currently default GPT entry array size is 80h bytes. Since one sector is 200h
bytes, one sector can hold 4 entries. According to the specification by GPT,
up to 128 entries are allowed; thus we need one sector for PTHDR, and 32
sectors for partition entry array in BPT at minimum.
Minimum Reserved(Actual)
PMBR + PPT + Entries array: 1+1+32 2047
PPT + Entries array: 1+32 1
I am aware of linux limitation of up to 16 partitions per HDD due to Linux
Device List.
Your current implementation reserves only 1 sector for BPT, but clearly it is
not enough.
Toshi Aiyama
A boot selector developer
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