[dm-devel] LUKS2 - RAID0 - NVME : alignment issue

[Ondrej Kozina]

On 10/12/2018 01:56 PM, laurent cop wrote:
> Hello,
> 
> I have trouble while in top of the stack :
> mkfs.ext4 /dev/mapper/raid0luks2
> /dev/mapper/raid0luks2 alignement is offset by 147456 bytes
> This may result in very poor performance (re-) partitioning is suggested.
> I have the same pb with mkfs.xfs
> 
> I am using following scheme:
> 
> LUKS2           => created with cryptsetup -v luksFormat --type luks2 
> /dev/md127 --cipher aes-gcm-random --integrity aeae

There's a bug in align offset calculations in cryptsetup for LUKS2 
format. It'll get fixed with future 2.0.5 release.

Provided you don't have real data on the LUKS2 device already...could 
you provide us with --debug output from the luksFormat action run again? 
It'd help me to find out if it gets fixed with commit dd36d56d472e.

Regards
O.

> RAID 0           => created with mdadm chunk=32
> 3 Disks *NVME* => partition with gdisk (fist sector : 2048)
> 
> I got this information with lsblk -t for each 3 disks, i got the same 
> information.
> nvmeXn1
>         -> NvmeXn1p1                                 ALIGN = 0
>                    -> md127                               ALIGN = 0
>                             -> raid0luks2_dif           ALIGN = 147456
>                                         -> raid0luks2     ALIGN = 147456
> 1) How can I solve my alignment issue?
> 2) Is it normal to have low performances while writing with dd. I was 
> using LUKS previously and I got only one dev mapper. Now I got 2. Does 
> it have a big impact on performances?
> 
> Kind regards.
> 
> 
> --
> dm-devel mailing list
> dm-devel at redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>