Re: [PATCH v6 04/28] btrfs: disallow RAID5/6 in HMZONED mode

Josef Bacik
2019-12-13T20:39:16Z

On 12/12/19 11:08 PM, Naohiro Aota wrote:
> Supporting the RAID5/6 profile in HMZONED mode is not trivial. For example,
> non-full stripe writes will cause overwriting parity blocks. When we do a
> non-full stripe write, it writes to the parity block with the data at that
> moment. Then, another write to the stripes will try to overwrite the parity
> block with new parity value. However, sequential zones do not allow such
> parity overwriting.
>
> Furthermore, using RAID5/6 on SMR drives, which usually have a huge
> capacity, incur large overhead of rebuild. Such overhead can lead to higher
> to higher volume failure rate (e.g. additional drive failure during
> rebuild) because of the increased rebuild time.
>
> Thus, let's disable RAID5/6 profile in HMZONED mode for now.
>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef