From mboxrd@z Thu Jan 1 00:00:00 1970 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 92C6C10087C8 for ; Thu, 30 Jul 2020 20:49:43 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) (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 39107185A797 for ; Thu, 30 Jul 2020 20:49:43 +0000 (UTC) Message-Id: <1k1FUf-0008Bw-6B@mx1.helsinki.tools> From: =?utf-8?q?Janne_He=C3=9F?= In-Reply-To: <20200714160556.GA16281@redhat.com> Date: Thu, 30 Jul 2020 22:49:37 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: Re: [linux-lvm] =?utf-8?q?RAID-less_parity=3F?= 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="windows-1252" To: LVM general discussion and development Cc: =?utf-8?q?Janne_He=C3=9F?= Hi, Am Dienstag, 14. Juli 2020 18:05 CEST, schrieb David Teigland :=20 =20 > On Mon, Jul 13, 2020 at 04:34:52PM +0200, Janne He=C3=9F wrote: > > However some of my systems are single-disk systems. For those, RAIDs are > > not possible so I was thinking if LVM has some support for single-PV > > setups with parity on the same PV. >=20 > Hi, >=20 > We didn't include integrity+linear because we didn't see much value in it, > since it would require going to backups in case of an integrity failure. >=20 > > While this is probably a niche feature right now, I can see other > > projects like Stratis benefit from the integrity checks provided by > > dm-integrity (and dm-crypt in the future) to detect (and thanks to > > parity fix) bit rots. >=20 > dm-integrity will detect but not fix bit rot. This is where I see a benefit from having some parity on the LVM level. With dm-integrity spotting bit-rots and reporting errors to LVM, LVM can recover the blocks with parity information. This recovery procedure would give more feature parity to ZFS which I'm currently migrating from for a LVM-based solution. >=20 > > So is there any way to get a parity setup with the current state of LVM? > > I was thinking of a RAID-4 with one PV but the current tooling (more > > specifically lvcreate) doesn't let me do that. >=20 > It's not currently possible. We had an implementation for this we could > bring back if there is enough interest, so we'd like to hear more about > how this would be useful for you and others. I think this would be beneficial for a lot of users since it allows spotting and correcting bit-rots which is currently not possible other than using ZFS or RAID as far as I know. >=20 > Thanks, > Dave >=20 > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ >=20 =20 Thanks, Janne