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Mon, 11 May 2020 15:42:45 -0700 (PDT) To: Alberto Bursi , Zygo Blaxell , Steven Fosdick Cc: Btrfs BTRFS , Rich Rauenzahn References: <20200504230857.GQ10769@hungrycats.org> <20200511050635.GT10769@hungrycats.org> <69847faf-5fb3-9eac-b819-373a0f814044@gmail.com> From: Phil Karn Autocrypt: addr=karn@ka9q.net; keydata= mQENBEw2mJ4BCADELiPsLFHDwapoSU7d2xNHxmwzzrFUCZWhO34kM6G5+o9GUNmGgMQ0BmXp I6hx77HHnrj9FC6kWh/bxBt3+o8HW+NTWzJSvf6kW7ThaNt7v9iewkS23JOMarAZs4qy6MhT 1RW1/yWY7RimWxrmkKPTKKa0Ad4CWT6fcP3t+doqGslSQIeoTh0C33ZT+LY59Wcr224iXohN 4Uu/nFe4yAHjtA+4Sesveo3Tyi8cbOgkcO6vij+pXesCcuhtGMlnE2dxRqbenrfVGLUVxNug LkQdLWezaGGm+dcjWYk1xjtaDnsCpVaYCMsfYNADQPJAjAFu37pVdoXhseVXfzOUN2EXABEB AAG0GVBoaWwgS2FybiA8a2FybkBrYTlxLm5ldD6JATgEEwECACIFAkw2mJ4CGwMGCwkIBwMC BhUIAgkKCwQWAgMBAh4BAheAAAoJEPFOQ1TtRjRGU98H/Atsb/N4lNbzNdzdIRcHD9XgCEa1 UdR4mxgjwvLxS1nYRNdHwfTxvA5nxWfMx/0CB26VaNFdI3lkg/S0vYsSUu6M7l8Zb8v4JMyU 4B4yvkFHZ3II5oilzIMa3e2cMfDz7TSwO1JcXyI5y9vHnvH65/LQF+QojDgzf3vXKiNdTXJp 3nEa5IgMAB0rcSNsXFx8xbHi8s5niL9+1I7XTPvVMeXrMe8h4AG1nM/dK96WwmV+tLyXKYXn xVeb9F4X9CNQbkn/xAH+egvKHHT3V7K9cAhrDfu9Qwpo7zKk/akBpLWG2kmkTOfhXjm3UQhv MVgDmpeQIYa1HgAsKrsDQMzrIFm5AQ0ETDaYngEIAJmFdm0MmENzLEosD1FvGPJleWDYb0ah 8dOk4XUug1RhW40f7AsugT75pKs9PolXt92920GdU727X3Jpgdj4kLDtIQA0KZrOXiEOZjIZ WcROAyvTGyMs/P7Um1AGNM161Ga6/Wtlc076FN7EUQtzPbthH26M3lGWUX0Ccls/8Ep4qbnF IrMRBxjaxKbqfKPTeU10pDykzA7s5hiNe7qaegvqD6YLseZ+6FqCn988YnLiIaFeNbWxUY5G spjAsfesnAmpn5vhUqAGiizkNlAMIN31xvpLd93oM4/vORszIuN1UP2RlxL3s30BncZl2XOd Mk1/59Sy70zVqF1ANyMrA18AEQEAAYkBHwQYAQIACQUCTDaYngIbDAAKCRDxTkNU7UY0Rszt B/9ZPH9xw47lPkVJRbhgf0G7fdsxsyiuouAqOKklUNFSy4+qeGomjwE6YvdMybwGtaUGla7t 2mDzrva+7Gzb0inXIgmahQPmM16F3GVxGoFL+QJ+7gD8Hco6e0/2kju7ZREDE7SOEwKb3lhD eNLccfX2AqAHfCT/LVLbgBpMRmwUJQThM+33Z2L9BqIM3awj2mOTmeDumpxiDfroU90mGc9c pXe4YrNIkL/N8eMzLe1bpu+mpPCiIrEO+dFA7N8jjVcOCQ4Lr8sU6cOsEdkaACZiNFKT99eb NkKigK8sEkDZc/AKhPCEsnaZpwBZPScOL88LLi7FHj9Osznt+uhWfbLe Subject: Re: Western Digital Red's SMR and btrfs? Message-ID: <9bbad15c-1bd1-e91a-ae50-bb1e643c19e2@ka9q.net> Date: Mon, 11 May 2020 15:42:44 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <69847faf-5fb3-9eac-b819-373a0f814044@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 5/11/20 14:13, Alberto Bursi wrote: > > Afaik drive-managed SMR drives (i.e. all drives that disguise > themselves as non-SMR) are acting like a SSD, writing in empty "zones" > first and then running garbage collection later to consolidate the > data. TRIM is used for the same reasons SSDs also use it. > This is the way they are working around the performance penalty of > SMR, as it's the same limitation NAND flash also has (you can write > only a full cell at a time). > > See here for example > https://support-en.wd.com/app/answers/detail/a_id/25185 > > -Alberto Right, I understand that (some?) SMR drives support TRIM for the same reason that SSDs do (well, a very similar reason). My question was whether there'd be any reason for a NON-SMR drive to support TRIM, or if TRIM support necessarily implies shingled recording. I didn't know shingled recording was in any general purpose 2.5" spinning laptop drives like mine, and there's no mention of SMR in the HGST manual. Phil