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([2620:10d:c091:480::4e65]) by smtp.gmail.com with ESMTPSA id i2sm3555499qte.87.2019.12.13.08.21.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Dec 2019 08:21:51 -0800 (PST) Subject: Re: [PATCH v6 04/28] btrfs: disallow RAID5/6 in HMZONED mode To: Naohiro Aota , linux-btrfs@vger.kernel.org, David Sterba Cc: Chris Mason , Nikolay Borisov , Damien Le Moal , Johannes Thumshirn , Hannes Reinecke , Anand Jain , linux-fsdevel@vger.kernel.org References: <20191213040915.3502922-1-naohiro.aota@wdc.com> <20191213040915.3502922-5-naohiro.aota@wdc.com> From: Josef Bacik Message-ID: <460f3205-419e-63cf-376b-ddc2e2e88689@toxicpanda.com> Date: Fri, 13 Dec 2019 11:21:50 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20191213040915.3502922-5-naohiro.aota@wdc.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org 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 > Signed-off-by: Naohiro Aota Reviewed-by: Josef Bacik Thanks, Josef