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Re: Talking about RAID - disks with same id

deloptes <deloptes@xxxxxxxxx> writes:

> Hi,
> I noticed recently by accident that when I read/write from the oldest raid
> disks I have - only one of the tray leds blinks. Of course the led could be
> damaged, but rather not, so looking into it I found that both disks in
> question return same UUID. So I am concerned now that I don't have any true
> RAID there and that there is very important data on those disks.
> How is this possible and how to solve it - I would simply add 3rd 500MB disk
> to the raid and remove one of the others, but still what is the impact of
> this (stupid) coincidence ...
> # blkid /dev/sdf
> /dev/sdf: PTUUID="13e17ac7" PTTYPE="dos"
>                   ^^^^^^^^
> # blkid /dev/sdg
> /dev/sdg: PTUUID="13e17ac7" PTTYPE="dos"
>                   ^^^^^^^^
> # blkid /dev/sda
> /dev/sda: PTUUID="4184002e" PTTYPE="dos"
> # blkid /dev/sdb
> /dev/sdb: PTUUID="9570a766" PTTYPE="dos"
> # blkid /dev/sdd
> /dev/sdd: PTUUID="d898a14c" PTTYPE="dos"
> # blkid /dev/sde
> /dev/sde: PTUUID="b6346d5e" PTTYPE="dos"
> # blkid /dev/sdf1
> /dev/sdf1: UUID="5427071b-25c8-fff8-476d-ff8c9852b714"
> TYPE="linux_raid_member" PARTUUID="13e17ac7-01"
> # blkid /dev/sdg1
> /dev/sdg1: UUID="5427071b-25c8-fff8-476d-ff8c9852b714"
> TYPE="linux_raid_member" PARTUUID="13e17ac7-01"

This is normal.  It's the identical UUIDs that tell the system that the
partitions go into the same RAID array.

Here's what I see when I look at my RAID disks:

/dev/sda2: UUID="67d3c233-96a0-737c-5f88-ed9b936ea3ae" UUID_SUB="48b56869-6f19-21b9-283f-3eee3ac90cf8" LABEL="snowball:1" TYPE="linux_raid_member" PARTUUID="3bb3729a-528b-4384-b6a5-b6d9e148ed2a"
/dev/sdb2: UUID="67d3c233-96a0-737c-5f88-ed9b936ea3ae" UUID_SUB="1f48f805-4173-78cd-1f52-957920f66335" LABEL="snowball:1" TYPE="linux_raid_member" PARTUUID="1bdd3893-9346-49d2-8292-a61075ad0c5e"

and here's the relevant line in my /etc/mdadm/mdadm.conf
ARRAY /dev/md/1  metadata=1.2 UUID=67d3c233:96a0737c:5f88ed9b:936ea3ae name=snowball:1

But...  if this data is that important, you should be running backups.
RAID is to keep you running if a disk fails, it isn't to keep you from
losing data.