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Thread-Topic: [LSF/MM/BPF TOPIC] durability vs performance for flash devices (especially embedded!) 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR04MB7081.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: e411edc3-e4ac-4c88-a6b8-08d92ba50654 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Jun 2021 00:16:42.4170 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: S/zzG0vT0El9sR6M1/huxy2yL0b5QdsBxsMkhYvdCJ6IJvicCECoYbvdZwuCejgCEopKCF1KNL807OTbbo0uUA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR04MB4012 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2021/06/10 3:47, Bart Van Assche wrote:=0A= > On 6/9/21 11:30 AM, Matthew Wilcox wrote:=0A= >> maybe you should read the paper.=0A= >>=0A= >> " Thiscomparison demonstrates that using F2FS, a flash-friendly file=0A= >> sys-tem, does not mitigate the wear-out problem, except inasmuch asit=0A= >> inadvertently rate limitsallI/O to the device"=0A= > =0A= > It seems like my email was not clear enough? What I tried to make clear= =0A= > is that I think that there is no way to solve the flash wear issue with= =0A= > the traditional block interface. I think that F2FS in combination with=0A= > the zone interface is an effective solution.=0A= > =0A= > What is also relevant in this context is that the "Flash drive lifespan= =0A= > is a problem" paper was published in 2017. I think that the first=0A= > commercial SSDs with a zone interface became available at a later time=0A= > (summer of 2020?).=0A= =0A= Yes, zone support in the block layer and f2fs was added with kernel 4.10=0A= released in Feb 2017. So the authors likely did not consider that as a solu= tion,=0A= especially considering that at the time, it was all about SMR HDDs only. No= w, we=0A= do have ZNS and things like SD-Express coming which may allow NVMe/ZNS on e= ven=0A= the cheapest of consumer devices.=0A= =0A= That said, I do not think that f2fs is not yet an ideal solution as is sinc= e all=0A= its metadata need update in-place, so are subject to the drive implementati= on of=0A= FTL/weir leveling. And the quality of this varies between devices and vendo= rs...=0A= =0A= btrfs zone support improves that as even the super blocks are not updated i= n=0A= place on zoned devices. Everything is copy-on-write, sequential write into= =0A= zones. While the current block allocator is rather simple for now, it could= be=0A= tweaked to add some weir leveling awareness, eventually (per zone weir leve= ling=0A= is something much easier to do inside the drive though, so the host should = not=0A= care).=0A= =0A= In the context of zoned storage, the discussion could be around how to best= =0A= support file systems. Do we keep modifying one file system after another to= =0A= support zones, or implement weir leveling ? That is *very* hard to do and= =0A= sometimes not reasonably feasible depending on the FS design.=0A= =0A= I do remember Dave Chinner talk back in 2018 LSF/MM (was it ?) where he=0A= discussed the idea of having block allocation moved out of FSes and turned = into=0A= a kind of library common to many file systems. In the context of consumer f= lash=0A= weir leveling, and eventually zones (likely with some remapping needed), th= is=0A= may be something interesting to discuss again.=0A= =0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=