Re: RAID5 up, but one drive removed, one says spare building, what now?

[Jun-Kai Teoh <kai.teoh@gmail.com>]

> On Nov 10, 2017, at 11:04 AM, Phil Turmel <philip@turmel.org> wrote:
> 
> On 11/10/2017 01:15 PM, Jun-Kai Teoh wrote:
> 
>> I'm backing up as much as I can, but I don't think I'll be able to 
>> back up everything. I can back up very little of the data, so I'm 
>> trying to prioritize carefully right now.
> 
> Ah, ok.  Well, after you get the important stuff backed up, you can
> add more devices as spares and try to let MD continue its grow and
> rebuild operations.  It might end up completing.

Again, pardon me if I sound super ignorant, I just want to do all of this right.

Do I just plug in another blank 4TB, and run "mdadm -A /dev/md126 /dev/sd[newdrive]" into it?

Or leave it as it is, and just ask it to continue growing with "mdadm -A -R", and *then* add a blank drive into the raid but don't ask it to grow?

> But don't add any more complete devices to the array -- use a partition
> that starts at 1MB and covers the rest of the device (default for most
> partition tools nowadays).

Where can I read about how to do this properly? I tried googling it but I'm pretty lost. Or what tool I should use etc.

> I recommend that when/if your array is stable again, you add one more
> spare (with partition) and then use mdadm's --replace operation to move
> complete-device members to the new member.  When each is done, take the
> newly freed device and partition it and do the next.  When you have no
> more complete-device members and have the last freed device partitioned,
> consider converting to raid6 with that spare.

I think I understand what you mean here, but it sounds like I need to figure out the top two parts first and that'll take me awhile.

I'll probably have questions again, later, haha.

I really appreciate all the support and patience from this list.

Y'all lifesavers.