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From: Gionatan Danti <g.danti@assyoma.it>
To: "LVM general discussion and development" <linux-lvm@redhat.com>,
	"Janne Heß" <janne+lvm@hess.ooo>
Subject: Re: [linux-lvm] RAID-less parity?
Date: Tue, 14 Jul 2020 17:15:20 +0200	[thread overview]
Message-ID: <13bd9503-6599-c6bb-83ab-4b427a2450e3@assyoma.it> (raw)
In-Reply-To: <1juzXg-0002Wp-5c@mx1.helsinki.tools>

On 7/13/20 4:34 PM, Janne Heß wrote:
> Hello everyone,
> 
> I'm currently testing dm-integrity and its use with LVM.
> For RAID 1,5,6 LVM should just be able to recover the RAID when integrity fails (and the block device returns a read error).
> 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.
> 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.
> 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.

Hi,
on current LVM implementation, the number of stripes can not exceed the 
number of physical device.

The only possibility I can think of is to partition your disk in 
multiple regions (ie: 3 partitions), adding them as PV to a new VG and 
the creating a RAID4/5 type volume.

Anyway, for good recovery chances you *need* physically different 
devices; otherwise, a catastrophic failure on your single device will 
eat all your data.

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

  reply	other threads:[~2020-07-14 15:17 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 14:34 Janne Heß
2020-07-14 15:15 ` Gionatan Danti [this message]
2020-07-14 16:05 ` David Teigland
2020-07-14 20:32   ` Gionatan Danti
2020-07-30 20:49   ` Janne Heß

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