On Sat, Aug 7, 2021 at 2:52 PM Roberto Ragusa <mail@xxxxxxxxxxxxxxxx> wrote:
>
> On 8/7/21 4:19 PM, lejeczek via users wrote:
>
> > $ -> lvcreate --type raid0 -i 4 -I 16 -n 0 -l 90%pv dellH200.InternalB /dev/sd{c..f}
> > and so on...
> The original poster wants to replace a 2 disk RAID-1 with a bigger 2 disk RAID-1,
> that is something very different than your suggestion to have a 4 disk RAID-0.
>
> The first link mentioned by José María Terry Jiménez is a good procedure for
> what we want to achieve.
> I would only point out that everybody tends to remove one of the drive and then
> add a new one, while you can instead grow the RAID-1 to 3 disks, add your new
> drive, then remove the old one, then add the second new one and remove the second
> old one, then (un)grow back to 2 drives and finally resize md and pv.
> In this way your array never works in degrade 1-disk mode.
> Of course nobody stops you from going to 4 disk RAID-1 (add, add, remove, remove).
>
> I usually do not create RAID-1 on the entire disk space, I prefer to partition
> into fixed size fragments (e.g. 4 470GB on a 2TB disk) and create many RAID-1
> out of partition couples to use as pv. In this way the new shiny 4TB disks are
> just giving me 8 additional 470GB pieces, I can create the new RAID-1s and pvs,
> add them to the vg and then use pvmove to decide where the data should be,
> eventually pvremoving the RAID-1 pieces on the old disks if I'm planning to
> physically remove them.
> Everything can be done online, and not even a powerloss is able to do any damage.
> Done this many many times on big storage servers.
>
While I agree with the "add the pvs to the vgs, pvmove data,
remove old pvs" approach, I would like to ask more about why you do
not use the entire disk for a raid, instead partition both drives in
many volumes and then create raid1 volumes using the respective
partitions in the two drives. Does that limit the damage due to HD
failure somehow better than a single partition?
> Regards.
> --
> Roberto Ragusa mail at robertoragusa.it
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