From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mimecast-mx02.redhat.com (mimecast03.extmail.prod.ext.rdu2.redhat.com [10.11.55.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 53D40112D19F for ; Tue, 15 Sep 2020 22:32:13 +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-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DB7EF800800 for ; Tue, 15 Sep 2020 22:32:13 +0000 (UTC) MIME-Version: 1.0 Date: Wed, 16 Sep 2020 00:32:06 +0200 From: Gionatan Danti In-Reply-To: <5070f4fa-81ad-9c9a-b0a7-8d5463ea09d3@redhat.com> References: <3f51904f43c45f8c1259f1b050402358@assyoma.it> <5070f4fa-81ad-9c9a-b0a7-8d5463ea09d3@redhat.com> Message-ID: <056d2d5dd9a7846a56971ce5f4cb3537@assyoma.it> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] lvmcache with vdo - inconsistent block size Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Zdenek Kabelac Cc: LVM general discussion and development Il 2020-09-15 20:34 Zdenek Kabelac ha scritto: > Dne 14. 09. 20 v 23:44 Gionatan Danti napsal(a): >> Hi all, >> I am testing lvmcache with VDO and I have issue with devices block >> size. >> >> The big & slow VDO device is on top of a 4-disk MD RAID 10 device >> (itself on top of dm-integrity). Over the VDO device I created a >> thinpool and a thinvol [1]. When adding the cache device to the volume >> group via vgextend, I get an error stating "Devices have inconsistent >> logical block sizes (4096 and 512)." [2] >> >> Now, I know why the error shows and what i means. However, I don't >> know how to force the cache device to act as a 4k sector device, >> and/if this is really required to cache a VDO device. >> >> My current workaround is to set VDO with --emulate512=enabled, but >> this can be suboptimal and it is not recommended. >> >> Any idea on what I am doing wrong? > > Hi > > LVM currently does not support mixing devices of different sector sizes > within > a single VG as it brings lot of troubles we have not yet clear vision > what > to do with all of them. Hi Zdenek, yes, I understand. What surprised me is that lvmvdo *can* be combined with caching, and it does not suffer from this issue. Can you elaborate on why it works in this case? > Also this combination of provisioned devices is not advised - since > you are combining 2 kind of devices on top of each other and it can be > a big problem > to solve recovery case. True. > On lvm2 side we do not allow to use 'VDO LV' as backend for thin-pool > device. I noticed it. However, from what I can read on RedHat docs, thinpool over VDO device should be perfectly fine (the other way around, not so much). > So ATM it's on a user to solve all the possible scenarios that may > appear on > such device stack. > > Zdenek Thanks. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8