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[PATCH] doc: 1MiB-alignment is not enough for cheap flash drives

From: Jim Meyering
Subject: [PATCH] doc: 1MiB-alignment is not enough for cheap flash drives
Date: Wed, 02 Jan 2013 12:56:20 +0100


>From 21be64fc6ef60a1e9dc7bc352131be58cc59d61d Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Wed, 2 Jan 2013 12:52:14 +0100
Subject: [PATCH] doc: 1MiB-alignment is not enough for cheap flash drives

* doc/parted.texi: Add an example that aligns to 4GiB, and
reference Arnd Bergman's LWN article.
 doc/parted.texi | 39 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/doc/parted.texi b/doc/parted.texi
index b8db19d..008c383 100644
--- a/doc/parted.texi
+++ b/doc/parted.texi
@@ -14,7 +14,7 @@ and manipulating partition tables.
 @ifnottex @c texi2pdf don't understand copying and insertcopying ???
 @c modifications must also be done in the titlepage
-Copyright @copyright{} 1999-2012 Free Software Foundation, Inc.
+Copyright @copyright{} 1999-2013 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -577,15 +577,44 @@ partition table.
 @item ufs
 @end itemize

+For example, the following creates a logical partition that will contain
+an ext2 file system.  The partition will start at the beginning of the disk,
+and end 692.1 megabytes into the disk.

 (parted) @kbd{mkpart logical 0.0 692.1}
 @end example

-Create a logical partition that will contain an ext2 file system.  The
-partition will start at the beginning of the disk, and end 692.1
-megabytes into the disk.
+Now, we will show how to partition a low-end flash
+device (``low-end'', as of 2011/2012).
+For such devices, you should use 4MiB-aligned address@hidden
+Cheap flash drives will be with us for a long time to
+come, and, for them, 1MiB alignment is not enough.
+Use at least 4MiB-aligned partitions.
+For details, see Arnd Bergman's article,
address@hidden://http://lwn.net/Articles/428584/} and its many comments.}.
+This command creates a tiny place-holder partition at the beginning, and
+then uses all remaining space to create the partition you'll actually use:
+$ @kbd{parted -s /dev/sdX -- mklabel msdos \}
address@hidden    mkpart primary fat32 64s 4MiB \}
address@hidden    mkpart primary fat32 4MiB -1s}
address@hidden example
+Note the use of @samp{--}, to prevent the following @samp{-1s} last-sector
+indicator from being interpreted as an invalid command-line option.
+The above creates two empty partitions.  The first is unaligned and tiny,
+with length less than 4MiB.
+The second partition starts precisely at the 4MiB mark
+and extends to the end of the device.
+The next step is typically to create a file system in the second partition:
+$ @kbd{mkfs.vfat /dev/sdX2}
address@hidden example

 @end deffn


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