From: Yves-Alexis Perez <corsac@debian.org>
To: Sven Eschenberg <sven@whgl.uni-frankfurt.de>, dm-crypt@saout.de
Subject: Re: [dm-crypt] Alignment issue with 4K disk
Date: Mon, 04 Jan 2016 23:20:46 +0100 [thread overview]
Message-ID: <1451946046.3914.13.camel@debian.org> (raw)
In-Reply-To: <568AEA2C.6010809@whgl.uni-frankfurt.de>
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On lun., 2016-01-04 at 22:54 +0100, Sven Eschenberg wrote:
> Hi,
>
> start=4194304 -> assumind this is in 512 byte blocks, the start sector
> is aligned to MByte boundary and thus 4k boundary.
>
> Anyway, if your device only has one partition which is encrypted with
> dm-crypt, set it up to start at sector 2048 (which should be default for
> parted, fdisk and so on). Pass align-payload 2048 during creation of the
> LUKS header, which will give you an MByte boundary and should always be
> okay.
>
> If the kernel still complains, then something else might be going wrong.
Right now I have:
root@scapa:~# lsblk -o +ALIGNMENT /dev/sdc
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT ALIGNMENT
sdc 8:32 0 931.5G 0 disk 0
└─sdc1 8:33 0 931.5G 0 part 512
└─scapa-backup 253:4 0 931.4G 0 crypt /mnt/scapa-backup -1
And:
scapa-backup: 0 1953336209 crypt aes-xts-plain64
0000000000000000000000000000000000000000000000000000000000000000 0 8:33 65536
root@scapa:~# fdisk -l /dev/sdc
Disk /dev/sdc: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 33553920 bytes
Disklabel type: gpt
Disk identifier: EBA98857-89BA-4B2C-8366-4A77A527A8E0
Device Start End Sectors Size Type
/dev/sdc1 65535 1953467279 1953401745 931.5G Linux filesystem
Partition 1 does not start on physical sector boundary.
[I'm a bit concerned with that, but since I'm using a GPT and not MBR it might
be related]
root@scapa:~# gdisk -l /dev/sdc
GPT fdisk (gdisk) version 1.0.1
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Found valid GPT with protective MBR; using GPT.
Disk /dev/sdc: 1953525168 sectors, 931.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): EBA98857-89BA-4B2C-8366-4A77A527A8E0
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 8-sector boundaries
Total free space is 123356 sectors (60.2 MiB)
Number Start (sector) End (sector) Size Code Name
1 65535 1953467279 931.5 GiB 8300 scapa-backup
Regards,
--
Yves-Alexis
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next prev parent reply other threads:[~2016-01-04 22:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-04 21:31 [dm-crypt] Alignment issue with 4K disk Yves-Alexis Perez
2016-01-04 21:54 ` Sven Eschenberg
2016-01-04 22:20 ` Yves-Alexis Perez [this message]
2016-01-04 22:41 ` Sven Eschenberg
2016-01-04 23:02 ` Sven Eschenberg
2016-01-05 10:14 ` Yves-Alexis Perez
2016-01-07 18:00 ` .. ink ..
2016-01-09 12:30 ` Milan Broz
2016-01-09 14:47 ` Sven Eschenberg
2016-01-10 0:25 Eugen Rogoza
2016-01-10 1:14 ` Sven Eschenberg
2016-01-10 4:30 ` Sven Eschenberg
2016-01-10 15:18 Eugen Rogoza
2016-01-10 15:37 Eugen Rogoza
2016-01-10 17:22 Eugen Rogoza
2016-01-10 19:13 ` Sven Eschenberg
2016-01-10 20:20 ` Eugen Rogoza
2016-01-10 21:00 ` Sven Eschenberg
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