3-disk RAID1 - only two disks active

3-disk RAID1 - only two disks active

am 15.11.2005 14:26:22 von vherva

I had two disks taken off from the three-disk raid set (hda,hdb,hdc - hdc
failed by itself, hdb was marked bad with raidsetfaulty). When the new disks
were added back to the set (with raidhotadd), only two of them became active
and one remained as a hot spare.

I there a way to reconfigure all three to become active again?

This is kernel 2.4.32-rc1.

> cat /proc/mdstat
Personalities : [raid1]
read_ahead 1024 sectors
md1 : active raid1 hdb1[2] hdc1[1] hda1[0]
102720 blocks [2/2] [UU]

md2 : active raid1 hdb2[2] hdc2[1] hda2[0]
1024064 blocks [2/2] [UU]

md3 : active raid1 hdb3[2] hdc3[1] hda3[0]
37955648 blocks [2/2] [UU]

unused devices:

> mdadm --detail /dev/md1
/dev/md1:
Version : 00.90.00
Creation Time : Fri May 10 13:42:55 2002
Raid Level : raid1
Array Size : 102720 (100.33 MiB 105.19 MB)
Device Size : 102720 (100.33 MiB 105.19 MB)
Raid Devices : 2
Total Devices : 3
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Mon Nov 14 23:17:03 2005
State : active
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1

UUID : d3f91d5b:5587896d:982609b1:c6a3e584
Events : 0.191

Number Major Minor RaidDevice State
0 3 1 0 active sync /dev/hda1
1 22 1 1 active sync /dev/hdc1

2 3 65 2 spare /dev/hdb1


> cat /etc/raidtab
raiddev /dev/md3
raid-level 1
nr-raid-disks 3
persistent-superblock 1
nr-spare-disks 0
device /dev/hda3
raid-disk 0
device /dev/hdb3
raid-disk 1
device /dev/hdc3
raid-disk 2
raiddev /dev/md2
raid-level 1
nr-raid-disks 3
persistent-superblock 1
nr-spare-disks 0
device /dev/hda2
raid-disk 0
device /dev/hdb2
raid-disk 1
device /dev/hdc2
raid-disk 2
raiddev /dev/md1
raid-level 1
nr-raid-disks 3
persistent-superblock 1
nr-spare-disks 0
device /dev/hda1
raid-disk 0
device /dev/hdb1
raid-disk 1
device /dev/hdc1
raid-disk 2
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Re: 3-disk RAID1 - only two disks active

am 16.11.2005 00:01:10 von NeilBrown

On Tuesday November 15, vherva@turing.netspan.fi wrote:
> I had two disks taken off from the three-disk raid set (hda,hdb,hdc - hdc
> failed by itself, hdb was marked bad with raidsetfaulty). When the new disks
> were added back to the set (with raidhotadd), only two of them became active
> and one remained as a hot spare.
>
> I there a way to reconfigure all three to become active again?

It looks from the details you gave that it never was a three-disk
set. It was only ever two-disk, possibly with a spare.

>
> This is kernel 2.4.32-rc1.

With a recent 2.6 kernel, you could
mdadm --grow --raid-disk=3 /dev/md1
but with a 2.4 kernel, the only option is to re-create the array:

mdadm --stop /dev/md1
mdadm --create /dev/md1 --level=1 --raid-disks=3 /dev/hda1 /dev/hdc1 missing
mdadm /dev/md1 --add /dev/hdb1

NeilBrown
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Re: 3-disk RAID1 - only two disks active

am 16.11.2005 04:23:09 von Ville Herva

On Wed, Nov 16, 2005 at 10:01:10AM +1100, you [Neil Brown] wrote:
> On Tuesday November 15, vherva@turing.netspan.fi wrote:
> > I had two disks taken off from the three-disk raid set (hda,hdb,hdc - hdc
> > failed by itself, hdb was marked bad with raidsetfaulty). When the new disks
> > were added back to the set (with raidhotadd), only two of them became active
> > and one remained as a hot spare.
> >
> > I there a way to reconfigure all three to become active again?
>
> It looks from the details you gave that it never was a three-disk
> set. It was only ever two-disk, possibly with a spare.

I can't dig up any hard evidence, but my impression is that it _was_ [UUU]
back when I had three disks in it the last time. That was in 2003, though.
It was created with the mentioned raidtab and 0.90 raidttools - shouldn't
that result into three active disks?

Later one disk was removed, and later one broken. Now two have been added
back.

Anyway, you may well be right, perhaps I misremember and it was 2 active + 1
one spare.

> > This is kernel 2.4.32-rc1.
>
> With a recent 2.6 kernel, you could
> mdadm --grow --raid-disk=3 /dev/md1
> but with a 2.4 kernel, the only option is to re-create the array:
>
> mdadm --stop /dev/md1
> mdadm --create /dev/md1 --level=1 --raid-disks=3 /dev/hda1 /dev/hdc1 missing
> mdadm /dev/md1 --add /dev/hdb1

Ok, thanks. One of the md's is rootfs, so I'll have to wait for a reboot to
try that.



-- v --

v@iki.fi

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