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Date: Tue, 14 Jul 2020 22:32:34 +0200
From: Gionatan Danti <g.danti@assyoma.it>
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Subject: Re: [linux-lvm] RAID-less parity?
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To: LVM general discussion and development <linux-lvm@redhat.com>
Cc: =?UTF-8?Q?Janne_He=C3=9F?= <janne+lvm@hess.ooo>

Il 2020-07-14 18:05 David Teigland ha scritto:
> 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=20
>> 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=20
> it,
> since it would require going to backups in case of an integrity=20
> failure.
>=20
> dm-integrity will detect but not fix bit rot.

Hi, I really think error detection has value by itself.
So I would suggest implementing it.

>=20
>> So is there any way to get a parity setup with the current state of=20
>> 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=20
> 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.

For this feature (parity+linear) I don't see much value: if a single=20
physical devices fails hard, all bet of recovery are off. However having=20
it can sometime be useful so, if implementing/maintenance cost are low,=20
why not?

Thanks.

--=20
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
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