* Assemble RAID on new machine but with missing devices
@ 2020-11-27 23:10 c.buhtz
2020-11-28 17:47 ` antlists
2020-11-29 17:05 ` Doug Herr
0 siblings, 2 replies; 4+ messages in thread
From: c.buhtz @ 2020-11-27 23:10 UTC (permalink / raw)
To: linux-raid
Hello,
I red some stuff about assembling mode for mdadm. But two points are
unclear for me.
1. Missing devices
I have two HDDs in a RAID1 - only data, no OS, on them. I want to
physical remove one HDD and plug it into a new server machine. Then I
want to bring the RAID1 online again on the new machine but with one
existing and one missing drive.
Background: When finished I will plug in a new fresh HDD as the second
one to the new server.
2. mdadm.conf
On the web I read sometimes about modifying mdadm.conf on the new
machine. But I do not understand why. If so. Why and what do I have to
modify in the mdadm.conf?
Kind
Christian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Assemble RAID on new machine but with missing devices
2020-11-27 23:10 Assemble RAID on new machine but with missing devices c.buhtz
@ 2020-11-28 17:47 ` antlists
2020-11-29 17:05 ` Doug Herr
1 sibling, 0 replies; 4+ messages in thread
From: antlists @ 2020-11-28 17:47 UTC (permalink / raw)
To: linux-raid
On 27/11/2020 23:10, c.buhtz@posteo.jp wrote:
> Hello,
>
> I red some stuff about assembling mode for mdadm. But two points are
> unclear for me.
>
> 1. Missing devices
> I have two HDDs in a RAID1 - only data, no OS, on them. I want to
> physical remove one HDD and plug it into a new server machine. Then I
> want to bring the RAID1 online again on the new machine but with one
> existing and one missing drive.
> Background: When finished I will plug in a new fresh HDD as the second
> one to the new server.
It's fairly certain that the array will - initially - refuse to run.
That's a safety feature - if an array is damaged while shut down, it
won't come back without intervention.
Put the single disk in your new system. As I say, it's unlikely it'll
start straight away. "cat /proc/mdstat" and if the array is there in a
failed state, stop it. Then you can re-assemble it and it should come up
degraded. All you have to do after that is replace the non-existent
drive with your new replacement, and you'll have a functioning array.
>
> 2. mdadm.conf
> On the web I read sometimes about modifying mdadm.conf on the new
> machine. But I do not understand why. If so. Why and what do I have to
> modify in the mdadm.conf?
>
If you've even got one ...
I don't know the history of it, but the early arrays did not have
superblocks, so mdadm.conf - an ACCURATE - mdadm.conf was essential. Now
they've got superblocks, it's optional and - to the best of my knowledge
- none of my systems have mdadm.conf's.
Do you have a superblock? Preferably v1 (1.0, 1.1 or 1.2). If you do,
don't worry about it, it's old advice, and while it's good to have an
up-to-date mdadm.conf to tell *you* what's what, the system doesn't need it.
Cheers,
Wol
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Assemble RAID on new machine but with missing devices
2020-11-27 23:10 Assemble RAID on new machine but with missing devices c.buhtz
2020-11-28 17:47 ` antlists
@ 2020-11-29 17:05 ` Doug Herr
1 sibling, 0 replies; 4+ messages in thread
From: Doug Herr @ 2020-11-29 17:05 UTC (permalink / raw)
To: linux-raid
On Sat, 28 Nov 2020 00:10:14 +0100, c.buhtz wrote:
> Then I want to bring the RAID1 online again on the new machine but with
> one existing and one missing drive.
As example, after creating and then stopping md8 I restarted it with only
one of the members. Mdadm told me how to force it...
[root@wombat looptesting]# mdadm --assemble /dev/md8 /dev/loop1
mdadm: /dev/md8 assembled from 1 drive - need all 2 to start it (use --
run to insist).
[root@wombat looptesting]# mdadm --assemble /dev/md8 /dev/loop1 --run
mdadm: /dev/md8 has been started with 1 drive (out of 2).
--
Doug Herr
--
Doug Herr
^ permalink raw reply [flat|nested] 4+ messages in thread
* Assemble RAID on new machine but with missing devices
@ 2020-11-28 12:11 c.buhtz
0 siblings, 0 replies; 4+ messages in thread
From: c.buhtz @ 2020-11-28 12:11 UTC (permalink / raw)
To: linux-raid
Hello,
I red some stuff about assembling mode for mdadm. But two points are
unclear for me.
1. Missing devices
I have two HDDs in a RAID1 - only data, no OS, on them. I want to
physical remove one HDD and plug it into a new server machine. Then I
want to bring the RAID1 online again on the new machine but with one
existing and one missing drive.
Background: When finished I will plug in a new fresh HDD as the second
one to the new server.
2. mdadm.conf
On the web I read sometimes about modifying mdadm.conf on the new
machine. But I do not understand why. If so. Why and what do I have to
modify in the mdadm.conf?
Kind
Christian
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-11-29 17:06 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-11-27 23:10 Assemble RAID on new machine but with missing devices c.buhtz
2020-11-28 17:47 ` antlists
2020-11-29 17:05 ` Doug Herr
2020-11-28 12:11 c.buhtz
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