On Mon, Jul 31, 2017 at 06:52:24PM +0300, Dima Dvorcovoy wrote:
> I got in trouble trying to mount RAID0 drives from brocen HW
> controller. The mdadm utility is locked to 4k stripe minimum, but these
> drives have 1s (512bytes) stripes.
>
> Then, I dig into kernel and found there are no actual stripe limitation
> seems. So, all the limits are in mdadm code. I patched soure and all
> works ok.
> mdadm --build /dev/md0 --level=0 --chunk=1s --raid-devices=2 /dev/sdd
> /dev/sdc
>
> First: there are UNDOCUCMENTED option in --chunk, size could be given
> in sectors (s).
>
> Second: 1s used as INVALID_SECTORS constant. I changed it to 0xffff
>
> Third: The sector number is stored in K. I removes this division, maybe
> it is only for output.
>
> Where to connect with mdadm team to ask for changes? What I skipped to
> patch?
Cc: Jes
If we really want to do this, please limit it to raid0 now. I think there is
problem with 512B chunksize for raid5, raid10 probably is ok.
Thanks,
Shaohua
> [mdadm.h]
> 1737c1737
> < * a value for 'invalid'. Use '1'.
> ---
> > * a value for 'invalid'. Use '-1'.
> 1739c1739
> < #define INVALID_SECTORS 1
> ---
> > #define INVALID_SECTORS 0xffff
> [mdadm.c]
> 381,384c381,382
> < if (s.chunk == INVALID_SECTORS ||
> < s.chunk < 8 || (s.chunk&1)) {
> < pr_err("invalid chunk/rounding value: %s\n",
> < optarg);
> ---
> > if (s.chunk == INVALID_SECTORS) {
> > pr_err("invalid chunk/rounding value: %s\n",optarg);
> [Build.c]
> 387,388d384
> < /* Convert sectors to K */
> < s.chunk /= 2;
> 145c145
> < array.chunk_size = s->chunk*1024;
> ---
> > array.chunk_size = s->chunk*512;
> [Create.c]
> 696c696
> < info.array.chunk_size = s->chunk*1024;
> ---
> > info.array.chunk_size = s->chunk*512;
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