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

Question

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)

Answer 1

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)