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Mon, 09 Jan 2023 19:48:55 -0800 (PST) Received: from [10.254.157.45] ([139.177.225.228]) by smtp.gmail.com with ESMTPSA id z30-20020aa7991e000000b005898fcb7c2bsm2024082pff.170.2023.01.09.19.48.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Jan 2023 19:48:54 -0800 (PST) Message-ID: <82a25856-bba4-8f9f-a5f5-4a3cd2d65200@bytedance.com> Date: Tue, 10 Jan 2023 11:48:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 To: Zdenek Kabelac , LVM general discussion and development References: <930cea69-8e7a-d0df-a48c-93e7a668be2f@redhat.com> <2b1466c2-f545-d06a-6ce4-d420ed038ad1@gmail.com> <255eaaae-e30b-2e69-cc03-38ca34902d16@redhat.com> From: Zhiyong Ye In-Reply-To: <255eaaae-e30b-2e69-cc03-38ca34902d16@redhat.com> X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mailman-Approved-At: Tue, 10 Jan 2023 08:00:09 +0000 Subject: Re: [linux-lvm] [External] Re: The feasibility of implementing an alternative snapshot approach X-BeenThere: linux-lvm@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: LVM general discussion and development Errors-To: linux-lvm-bounces@redhat.com Sender: "linux-lvm" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Hi Zdenek, Thank you for your patience and explanations. I learned a lot from our discussions and thank you again for your help. Regards Zhiyong On 1/10/23 6:18 AM, Zdenek Kabelac wrote: > Dne 09. 01. 23 v 7:21 Zhiyong Ye napsal(a): >> Hi Zdenek, >> >> Thank you for your detailed answer. >> >> For the thin snapshot I will use the latest version of kernel and lvm >> for further testing. I want to use both snapshot methods (thin and >> thick) in the production environment. But if the thick snapshot is >> only still in the maintenance phase, then for thick lv I have to see >> if there is any other way to accomplish the snapshot function. > > FYI - there are still some delays with up-streaming of the latest > improvement patches - so stay tuned for further speedup gains & IO > throughput with thin provisioning) > > By the maintenance phase for old thick snapshot I mean - the development > of the existing thick snapshot target is basically done - the format is > very ancient and cannot be changed without major rewrite of the whole > snapshot target as such - and that's what we've made with newly > introduced thin-provisioning target which addressed many shortcomings of > the old dm-snapshot target. > >> I use lvm mainly for virtualized environments. Each lv acts as a block >> device of the virtual machine. So I also consider using qemu's own >> snapshot feature. When qemu creates a snapshot, the original image >> used by the virtual machine becomes read-only, and all write changes >> are stored in the new snapshot. But currently qemu's snapshots only >> support files, not block devices. > > Depending on the use-case it might matter to pick the best fitting > chunk-size. > i.e. if the changes are 'localized' in the filesystem areas to match > thin-pool chunks (also selection of the filesystem itself might be part > of equation here) - even if you use snapshots a lot, you may eventually > get better result with bigger chunks like 128k or even 256k size instead > of default 64K. > > Regards > > Zdenek > _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/