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Vrenn
Guru
Joined: 15 Dec 2004
Posts: 318
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 Posted: Thu Jul 03, 2014 5:43 pm Post subject: [solved] 4k disk alignment confusion |
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Dear Gentoo Experts. When I was setting up my laptop I probably made some mistakes.
The first is my too small boot-partition, I know.
On the 4k-alignment I thought it was matching: | Code: | Disk /dev/sda: 698,7 GiB, 750156374016 bytes, 1465149168 sectors
Units: Sektoren of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x8307eef8
Partition 1 does not start on physical sector boundary.
Gerät Boot Start Ende Blocks Id System
/dev/sda1 63 80324 40131 de Dell Utility
/dev/sda2 * 81920 20496383 10207232 7 HPFS/NTFS/exFAT
/dev/sda3 20496384 750415871 364959744 7 HPFS/NTFS/exFAT
/dev/sda4 750415872 1465149167 357366648 5 Extended
/dev/sda5 * 750417920 750483455 32768 83 Linux
/dev/sda6 750485504 767483903 8499200 82 Linux swap / Solaris
/dev/sda7 767485952 1465149167 348831608 83 Linux |
using Dell Partition(1), recover(2) windows7(3) and Gentoo in the extended.
Then I was reading that the Partition offset on an 4k drive has to be divided by 4096 without comma.
sda7 is 767485952 / 4096 = 187 374,5 leaving ,5!
As ext4 uses 4096 too that partition seems to have a bad alinment.
http://wiki.hetzner.de has an example for correct alignment: | Code: | | /dev/sda3 5244928 1465149167 729952120 fd Linux raid autodetect |
5244928 / 4096 = 1 280,5. another 0.5!
Can you help me please where is the error: on my disk or in my brain?
I am not only using Gentoo for "full speed", rather for full understanding!
parted /dev/sda align-check opt 7 tells me "7 aligned". but aligned on logical 512 or physical 4096?
Do I need to kill my boot (sda5, for being so dump sparing on the wrong place), or my root to?
I want to do it right.
Thank you for any help.
_________________
With nice greetings
Vrenn
Last edited by Vrenn on Thu Jul 03, 2014 7:10 pm; edited 1 time in total |
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ulenrich
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Joined: 10 Oct 2010
Posts: 1480
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| Posted: Thu Jul 03, 2014 7:00 pm Post subject: |
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| Code: | ~$ echo "767485952 * 512 / 4096"|bc -l
95935744.00000000000000000000 |
seems ok |
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Vrenn
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Joined: 15 Dec 2004
Posts: 318
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| Posted: Thu Jul 03, 2014 7:10 pm Post subject: |
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" * 512" forgot fdisk tells me sectors, found error: my brain.
Thank you!
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With nice greetings
Vrenn |
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