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Date: Fri, 29 Jun 2012 16:24:01 +0300 (EEST)
From: Sayetsky Anton <vsjcfm@gmail.com>
Reply-To: Sayetsky Anton <vsjcfm@gmail.com>
To: FreeBSD-gnats-submit@freebsd.org
Cc:
Subject: gpart: partition alignment doesn't works on MBR
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X-GNATS-Notify:

>Number:         169542
>Category:       bin
>Synopsis:       gpart(8): partition alignment doesn't works on MBR
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jun 29 13:30:13 UTC 2012
>Closed-Date:    
>Last-Modified:  Wed Feb  5 19:50:00 UTC 2014
>Originator:     Sayetsky Anton
>Release:        FreeBSD 8.3-RELEASE-p1 amd64
>Organization:
>Environment:
System: FreeBSD jw.local 8.3-RELEASE-p1 FreeBSD 8.3-RELEASE-p1 #0 r235504: Wed May 16 14:33:18 EEST 2012 root@j.local:/tmp/obj/mnt/garbage/build/src/sys/JASONW amd64
>Description:
Alignment values computed by gpart are incorrect when using MBR scheme.
When using GPT - they are correct.
As wee can see below, alignment & size of partitions isn't divideable by 8 when using "-a 4k"
>How-To-Repeat:
********************* MBR **************************
root@jw:~# mdconfig -s 2048m
md0
root@jw:~# gpart create -s mbr md0
md0 created
root@jw:~# gpart show md0
=> 63 4194241 md0 MBR (2.0G)
63 4194241 - free - (2G)

root@jw:~# gpart add -a 4k -t freebsd -s 100m md0
md0s1 added
root@jw:~# gpart add -a 4k -t freebsd md0
md0s2 added
root@jw:~# gpart show md0
=> 63 4194241 md0 MBR (2.0G)
63 63 - free - (31k)
126 204687 1 freebsd (100M)
204813 63 - free - (31k)
204876 3989412 2 freebsd (1.9G)
4194288 16 - free - (8.0k)
********************* MBR **************************

********************* GPT **************************
root@jw:~# mdconfig -s 2048m
md0
root@jw:~# gpart create -s gpt md0
md0 created
root@jw:~# gpart add -a 4k -t freebsd -s 100m md0
md0s1 added
root@jw:~# gpart add -a 4k -t freebsd md0
md0s2 added
root@jw:~# gpart show md0
=>     34  4194237  md0  GPT  (2.0G)
      34        6       - free -  (3.0k)
      40   204800    1  freebsd  (100M)
  204840  3989424    2  freebsd  (1.9G)
 4194264        7       - free -  (3.5k)
********************* GPT **************************
>Fix:

>Release-Note:
>Audit-Trail:

From: Chris Whitehouse <cwhiteh@onetel.com>
To: bug-followup@FreeBSD.org, vsjcfm@gmail.com
Cc:  
Subject: Re: bin/169542: gpart(8): partition alignment doesn&#39;t works on
 MBR
Date: Wed, 05 Feb 2014 19:44:16 +0000

 I think this also affects gpart backup and restore of mbr partitions. 
 Using gpart backup redirected to a file, then gpart restore from the 
 same file results in a different layout.
 
 See
 http://lists.freebsd.org/pipermail/freebsd-questions/2014-February/256009.html
 
 Chris
>Unformatted:
