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 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CEE0BC43334 for ; Tue, 14 Jun 2022 07:11:20 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-222-SL5eUUXmNDGM9CQ8_rdvOQ-1; Tue, 14 Jun 2022 03:11:16 -0400 X-MC-Unique: SL5eUUXmNDGM9CQ8_rdvOQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 44BA6101E985; Tue, 14 Jun 2022 07:11:14 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (unknown [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E1BE2166B26; Tue, 14 Jun 2022 07:11:11 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id AE055194706F; Tue, 14 Jun 2022 07:11:10 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 265361947067 for ; Tue, 14 Jun 2022 07:11:10 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id 135C11121319; Tue, 14 Jun 2022 07:11:10 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast06.extmail.prod.ext.rdu2.redhat.com [10.11.55.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0F7F51121314 for ; Tue, 14 Jun 2022 07:11:10 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ED6BE185A7BA for ; Tue, 14 Jun 2022 07:11:09 +0000 (UTC) Received: from plutone.assyoma.it (host195-56-237-212.serverdedicati.aruba.it [212.237.56.195]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-670-5rWfLX8uNYW7bto7nIAFuw-1; Tue, 14 Jun 2022 03:11:07 -0400 X-MC-Unique: 5rWfLX8uNYW7bto7nIAFuw-1 Received: from webmail.assyoma.it (localhost [IPv6:::1]) by plutone.assyoma.it (Postfix) with ESMTPA id D91BB1D59AA6; Tue, 14 Jun 2022 09:04:02 +0200 (CEST) MIME-Version: 1.0 Date: Tue, 14 Jun 2022 09:04:02 +0200 From: Gionatan Danti To: LVM general discussion and development In-Reply-To: <9c22b11a-b539-1974-7994-6835eea82bfd@bytedance.com> References: <9c22b11a-b539-1974-7994-6835eea82bfd@bytedance.com> User-Agent: Roundcube Webmail/1.4.13 Message-ID: X-Sender: g.danti@assyoma.it 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 2.78 on 10.11.54.3 Subject: Re: [linux-lvm] Why is the performance of my lvmthin snapshot so poor 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 Cc: Zhiyong Ye Errors-To: linux-lvm-bounces@redhat.com Sender: "linux-lvm" X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-lvm-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Il 2022-06-13 10:49 Zhiyong Ye ha scritto: > The performance degradation after snapshotting is expected as writing > to a snapshotted lv involving reading the original data, writing it > elsewhere and then writing new data into the original chunk. But the > performance loss was so much more than I expected. Is there any way to > improve performance after creating a snapshot? Can I ask for your > help? This is the key point: when first writing to a new chunk, not only it needs to be allocated, but old data must be copied. This r/m/w operation transform an async operation (write) on a sync one (read), ruining performance. Subsequent writes to the same chunk does have the same issue. The magnitute of the slowdown seems somewhat excessive, though. When dealing with HDD pools, I remember a 3-5x impact on IOPs. Can you show the exact fio command and the parameters of your thin pool (ie: chunk size) and storage subsystem (HDD vs SSD, SATA vs SAS vs NVME)? Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8 _______________________________________________ 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/