[linux-lvm] extend raid5 - how if possible?

[Heinz Mauelshagen]

On 8/15/20 10:57 AM, lejeczek wrote:
> Hi guys
>
> In hope that experts roam this list I want to ask if it is
> possible to extend raid5.
> If I wanted to be specific, raid created this way:
>
> $ lvcreate -n raid5.1 -l 100%pv --stripes 5 --stripe-size 8
> ST2000_front.0 /dev/sdj /dev/sdk /dev/sdn /dev/sdo /dev/sdp
> /dev/sdq
>
> You can see I try to be specific about hard disks here. I
> hope that later I can add more of exact same hard disk to
> the system and extend such raid5.


As you consumed all capacity on those disks, you either got the option 
to extend using lvextend (though you don't need the same disk sizes but 
you'd need 6 more disks to be able to extend all the given raid5 stripes 
using lvextend)  -or-  you can lvconvert adding stripes to your given 
raid5 which will also grow the RaidLV size by the added stripe 
capacities.   In that later case of adding stripes, you'd have to deploy 
N additional disks (N = number of stripes to add) of the same or larger 
size than the ones you got.

Mind, you could also convert to e.g. raid6 in case your resilience 
requirements change which'll require another disk to store parity blocks.

Heinz

>
> many thanks, L.
>
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