On 4/16/20 6:30 PM, Coly Li wrote:
> Hi folks,
>
> When I try to create md raid5 array with 4 NVMe SSD (3 for raid array
> component disks, 1 for write log), the kernel is Linux v5.6 (not Linux
> v5.7-rc), I find the md raid5 array cannot start.
>
> I use this command to create md raid5 with writelog,
>
> mdadm -C /dev/md0 -l 5 -n 3 /dev/nvme{0,1,2}n1 --write-journal /dev/nvme3n1
>
> From terminal I have the following 2 lines information,
>
> mdadm: Defaulting to version 1.2 metadata
> mdadm: RUN_ARRAY failed: Invalid argument
>
> From kernel message, I have the following dmesg lines,
>
> [13624.897066] md/raid:md0: array cannot have both journal and bitmap
> [13624.897068] md: pers->run() failed ...
> [13624.897105] md: md0 stopped.
>
> But from /proc/mdstat, it seems an inactive array is still created,
>
> /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md127 : inactive nvme2n1[4](S) nvme0n1[0](S) nvme3n1[3](S)
> 11251818504 blocks super 1.2
>
> unused devices: <none>
>
> From all the information it seems when initialize raid5 cache the bitmap
> information is not cleared, so an error message shows up and raid5_run()
> fails.
>
> I don't have clear idea who to handle bitmap, journal and ppl properly,
> so I firstly report the problem here.
>
> So far I am not sure whether this is a bug or I do something wrong. Hope
> other people may reproduce the above failure too.
Hi Coly,
It looks like the mdadm that you're using added an internal bitmap
despite creating the array with a journal. I think that was fixed some
time ago. The kernel correctly does not allow starting the array with
bitmap and journal (or ppl). You can assemble this now with:
mdadm -A /dev/md0 /dev/nvme[0-3]n1 --update=no-bitmap
You can also explicitly tell mdadm not to add a bitmap when creating an
array using "--bitmap=none".
Regards,
Artur
