[solved] fdisk alignment not sticking on /dev/sda1

demian · 2010-03-17 22:43:59

Hey everyone.

There are several statements that SSDs should be properly aligned.
So i went ahead and aligned my Intel X25-M following this guide on the OCZ forums.
After partitioning the SSD with fdisk using proper alignment, i confirmed via 'fdisk -l' and 'fdisk -lu' that the alignment is correct.
My next step was installing Windows Vista X86_X64, where AS Benchmark again confirmed a proper alignment (128 K as suggested by Theodore Ts'o or 512 K, as suggested in the guide linked above, i tried both).

However, when i checked with fdisk again to confirm the alignment once more, the alignment for /dev/sda1 seems to have shifted. I also get the message, that partition 2 doesn't end on a cylinder boundary.

Right now, it should be 32 heads and 32 sectors per track to result in a 512 K alignment. But fdisk shows 255 heads and 63 sectors/track for /dev/sda1, which is, from what i understand, the standard used by linux. The other partitions seem to be just fine.
I've read that there might be an issue with partition 1 shifting but i also heard it could by avoided by starting partition 1 on cylinder 2 instead of cylinder 1. Unfortunately, that doesn't change anything for me.

Can anyone tell me what i did wrong?

Regards,
demian

Here's the bad output:
fdisk -l

Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x3d26f824

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        1567    12583424    7  HPFS/NTFS
/dev/sda2            1567        9730    65566720    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sda5            1567        2220     5243376   83  Linux
/dev/sda6            2220        2742     4194800   83  Linux
/dev/sda7            2742        9730    56128496    7  HPFS/NTFS

printed partition table in expert mode

Disk /dev/sda: 255 heads, 63 sectors, 9729 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
 1 80  16  17    0 254  63 1023       1024   25166848 07
 2 00  31  32 1023  31  32 1023   25167872  131133440 05
Partition 2 does not end on cylinder boundary.
 3 00   0   0    0   0   0    0          0          0 00
 4 00   0   0    0   0   0    0          0          0 00
 5 00  31  32 1023  31  32 1023         32   10486752 83
 6 00  31  32 1023  31  32 1023         32    8389600 83
 7 00  31  32 1023  31  32 1023         32  112256992 07

Last edited by demian (2010-06-19 09:38:32)

jimburnettva · 2010-03-18 14:28:39

Found this
http://thunk.org/tytso/blog/2009/02/20/ … lock-size/

Hope that helps.

demian · 2010-03-18 18:26:12

Thanks, but i knew that one. It doesn't really offer any help.

However, i found people who have the exact same issue:
http://www.ocztechnologyforum.com/forum … n&p=500030

It seems to be connected to the install routine of Windows 7 and Windows Vista.
Dunno how to fix it though.
Anyone here who's good with partition tables and the standards used by Windows?

danij3l · 2010-06-19 02:56:19

bump

same problem

demian · 2010-06-19 09:38:07

You can avoid it by using /dev/sda1 for /boot or swap. You should still start /dev/sda1 in cylinder 2 though.
Also, remember to adjust the offset of all the logical partitions in expert mode. Otherwise they'd start sector 32 as you can see in the bottom code tags in my first post.

For example, here's my current installation:

Disk /dev/sda: 80.0 GB, 80026361856 bytes
32 heads, 32 sectors/track, 152638 cylinders
Units = cylinders of 1024 * 512 = 524288 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x25168a91

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               2         402      205312   83  Linux
/dev/sda2   *         403       24979    12583424    7  HPFS/NTFS
/dev/sda3           24980      152638    65361408    5  Extended
/dev/sda5           24981       26517      786944   82  Linux swap / Solaris
/dev/sda6           26519       38806     6291456   83  Linux
/dev/sda7           38808       49047     5242880   83  Linux
/dev/sda8           49049      152638    53038080    7  HPFS/NTFS

Disk /dev/sda: 32 heads, 32 sectors, 152638 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
 1 00   0   1    1  31  32  401       1024     410624 83
 2 80   0   1  402  31  32 1023     411648   25166848 07
 3 00  31  32 1023  31  32 1023   25578496  130722816 05
 4 00   0   0    0   0   0    0          0          0 00
 5 00  31  32 1023  31  32 1023       1024    1573888 82
 6 00  31  32 1023  31  32 1023       1024   12582912 83
 7 00  31  32 1023  31  32 1023       1024   10485760 83
 8 00  31  32 1023  31  32 1023       1024  106076160 07

Disk /dev/sda: 80.0 GB, 80026361856 bytes
32 heads, 32 sectors/track, 152638 cylinders, total 156301488 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x25168a91

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            1024      411647      205312   83  Linux
/dev/sda2   *      411648    25578495    12583424    7  HPFS/NTFS
/dev/sda3        25578496   156301311    65361408    5  Extended
/dev/sda5        25579520    27153407      786944   82  Linux swap / Solaris
/dev/sda6        27154432    39737343     6291456   83  Linux
/dev/sda7        39738368    50224127     5242880   83  Linux
/dev/sda8        50225152   156301311    53038080    7  HPFS/NTFS

Regards,
demian

Last edited by demian (2010-06-19 09:42:35)

graysky · 2010-06-28 22:31:28

@demian - so the steps you used were:

1) fdisk -H 32 -S 32 /dev/sdX
2) create new partition table (lower case "o" in fdisk)
3) make a new partition starting on sector 2
4) assign a file system type
5) make the 2nd, 3rd, ...nth partition and assign their file systems
6) write changes and exit

Is it still your experience that /dev/sdX1 needs to be /boot and will become misaligned? I do NOT plan to install Windows at all. Just root (15 G) and home (remainder of SDD). I will keep my SSD as /dev/sdb keeping my HDD as /dev/sda. The HDD will contain /boot, swap, and /var (/tmp will be in memory).

Thanks for the info!

Last edited by graysky (2010-06-28 22:36:24)

Arch Linux

#1 2010-03-17 22:43:59

[solved] fdisk alignment not sticking on /dev/sda1

#2 2010-03-18 14:28:39

Re: [solved] fdisk alignment not sticking on /dev/sda1

#3 2010-03-18 18:26:12

Re: [solved] fdisk alignment not sticking on /dev/sda1

#4 2010-06-19 02:56:19

Re: [solved] fdisk alignment not sticking on /dev/sda1

#5 2010-06-19 09:38:07

Re: [solved] fdisk alignment not sticking on /dev/sda1

#6 2010-06-28 22:31:28

Re: [solved] fdisk alignment not sticking on /dev/sda1

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