From: Sven Eschenberg <sven@whgl.uni-frankfurt.de>
To: dm-crypt@saout.de
Subject: Re: [dm-crypt] Alignment issue with 4K disk
Date: Tue, 5 Jan 2016 00:02:43 +0100 [thread overview]
Message-ID: <568AFA13.2010208@whgl.uni-frankfurt.de> (raw)
In-Reply-To: <1451946046.3914.13.camel@debian.org>
Hi Alexis,
I stumbled over this line:
I/O size (minimum/optimal): 4096 bytes / 33553920 bytes
The latter resembles 65535 sectors (512 Byte logical ones), which
explains why the automated alignment was done at sector 65535. This
value seems extremely weird though.
You said the drive was external, connected how? USB maybe?
Can you take a look at hdparm -I /dev/sdc? Anything unusual there?
Regards
-Sven
Am 04.01.2016 um 23:20 schrieb Yves-Alexis Perez:
> 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,
>
>
>
> _______________________________________________
> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt
>
next prev parent reply other threads:[~2016-01-04 23:02 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
2016-01-04 22:41 ` Sven Eschenberg
2016-01-04 23:02 ` Sven Eschenberg [this message]
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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