From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wols Lists Subject: Re: [RFC] dm-bow working prototype Date: Thu, 25 Oct 2018 22:15:39 +0100 Message-ID: <5BD2327B.1040908@youngman.org.uk> References: <20181023212358.60292-1-paullawrence@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Paul Lawrence Cc: linux-raid@vger.kernel.org, dm-devel@redhat.com, Linux kernel List-Id: dm-devel.ids T24gMjUvMTAvMTggMTk6MTMsIFBhdWwgTGF3cmVuY2Ugd3JvdGU6Cj4+IEkgaGF2ZSBzb21lIHF1 ZXN0aW9ucyBhYm91dCBkbS1ib3c6Cj4+IOKAkyBIb3cgZmlsZSBzeXN0ZW0gYWdub3N0aWMgdGhp cyBmZWF0dXJlIGlzIHBsYW5uZWQgdG8gYmU/IFdoaWxlIGl0IGlzCj4+IGRlc2lnbmVkIHdpdGgg ZXh0NCBpbiBtaW5kLCBpcyBpdCBnb2luZyB0byB3b3JrIHdoZW4gdXNlZCBvdmVyIG90aGVyCj4+ IGZpbGUgc3lzdGVtcywgbGlrZSBGQVQgb3IgQlRSRlMgZm9yIGV4YW1wbGU/Cgo+IFNvIGxvbmcg YXMgdGhlIGZpbGUgc3lzdGVtIHN1cHBvcnRzIGZzdHJpbSwgaXQgc2hvdWxkIHdvcmsuIElmIHRo ZSBmaWxlCj4gc3lzdGVtIGNyZWF0ZXMgYSBsb3Qgb2YgY2h1cm4gc2F5IGJ5IHJ1bm5pbmcgZ2Fy YmFnZSBjb2xsZWN0aW9uLCBJJ2Qgbm90Cj4gcmVjb21tZW5kIGl0LiBBbmQgSSByZWFsbHkgZG9u J3Qgc2VlIHRoZSB1c2UgY2FzZSBpZiB0aGUgZmlsZSBzeXN0ZW0gaGFzCj4gYW55IHNvcnQgb2Yg c25hcHNob3QgY2FwYWJpbGl0eSAtIHRoYXQgd2lsbCBhbHdheXMgYmUgYSBzdXBlcmlvcgo+IHNv bHV0aW9uIHRvIGEgYmxvY2sgbGV2ZWwgb25lIElNTy4KClNvcnJ5IGZvciBiZWluZyBkZW5zZSwg YnV0IHdoeSBpcyB0aGlzIHBvc3RlZCB0byBsaW51eC1yYWlkLCB0aGVuPyBSYWlkCmRvZXMgbm90 IHN1cHBvcnQgZnN0cmltLCBhbmQgaXMgZmlsZXN5c3RlbS1hZ25vc3RpYy4KCkkgY2FuIGltYWdp bmUgcGVvcGxlIGhlcmUgYmVpbmcgaW50ZXJlc3RlZCwgYnV0IGl0IGZlZWxzIHRvIG1lIGFzIHRo b3VnaAp5b3VyIGZ1bmN0aW9uYWxpdHkgaXMgY29tcGxldGVseSBvcnRob2dvbmFsIHRvIHJhaWQu IFNvcnJ5LgoKQ2hlZXJzLApXb2wKCi0tCmRtLWRldmVsIG1haWxpbmcgbGlzdApkbS1kZXZlbEBy ZWRoYXQuY29tCmh0dHBzOi8vd3d3LnJlZGhhdC5jb20vbWFpbG1hbi9saXN0aW5mby9kbS1kZXZl bA== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC3B7ECDE46 for ; Thu, 25 Oct 2018 21:52:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 95B002083E for ; Thu, 25 Oct 2018 21:52:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95B002083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=youngman.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727706AbeJZG1R (ORCPT ); Fri, 26 Oct 2018 02:27:17 -0400 Received: from smtp.hosts.co.uk ([85.233.160.19]:38782 "EHLO smtp.hosts.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726174AbeJZG1Q (ORCPT ); Fri, 26 Oct 2018 02:27:16 -0400 X-Greylist: delayed 2236 seconds by postgrey-1.27 at vger.kernel.org; Fri, 26 Oct 2018 02:27:16 EDT Received: from [81.157.153.73] (helo=[192.168.1.82]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1gFmyi-0005Bd-Ac; Thu, 25 Oct 2018 22:15:40 +0100 Subject: Re: [RFC] dm-bow working prototype To: Paul Lawrence References: <20181023212358.60292-1-paullawrence@google.com> Cc: dm-devel@redhat.com, Linux kernel , linux-raid@vger.kernel.org From: Wols Lists Message-ID: <5BD2327B.1040908@youngman.org.uk> Date: Thu, 25 Oct 2018 22:15:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/10/18 19:13, Paul Lawrence wrote: >> I have some questions about dm-bow: >> – How file system agnostic this feature is planned to be? While it is >> designed with ext4 in mind, is it going to work when used over other >> file systems, like FAT or BTRFS for example? > So long as the file system supports fstrim, it should work. If the file > system creates a lot of churn say by running garbage collection, I'd not > recommend it. And I really don't see the use case if the file system has > any sort of snapshot capability - that will always be a superior > solution to a block level one IMO. Sorry for being dense, but why is this posted to linux-raid, then? Raid does not support fstrim, and is filesystem-agnostic. I can imagine people here being interested, but it feels to me as though your functionality is completely orthogonal to raid. Sorry. Cheers, Wol