Re: [linux-lvm] RAID-less parity?

[Gionatan Danti <g.danti@assyoma.it>]

Il 2020-07-14 18:05 David Teigland ha scritto:
> On Mon, Jul 13, 2020 at 04:34:52PM +0200, Janne Heß 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.
> 
> Hi,
> 
> 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.
> 
> 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.

> 
>> 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.
> 
> 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.

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

Thanks.

-- 
Danti Gionatan
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