* mdadm RAID1 with 3 disks active on 2 disks configuration
@ 2020-02-23 17:38 Aymeric
2020-02-23 20:40 ` antlists
0 siblings, 1 reply; 4+ messages in thread
From: Aymeric @ 2020-02-23 17:38 UTC (permalink / raw)
To: linux-raid
Hello,
I've a system with a RAID1 using two disks (sda + sdb) + 1 spare (sdc).
For some stupid reason (cable) the spare (sdc) became active and sda was
out the array.
I then added back sda to the RAID1 but now I've RAID1 with three active
disks and zero spare.
I don't understand why the spare device didn't switch back as spare
after sda have been rebuild.
I used the following command to add sda to the RAID1:
# mdadm /dev/md0 --add /dev/sda3
What did I do wrong here? And how to fix it? Do I have to set sdc to
faulty and add it back?
Thanks!
Here are the RAID1 status:
# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5]
[raid4] [raid10]
md0 : active raid1 sda3[2] sdc3[3](W)(R) sdb3[0]
976015360 blocks super 1.2 [2/3] [UU]
bitmap: 1/8 pages [4KB], 65536KB chunk
# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Sep 5 09:45:55 2018
Raid Level : raid1
Array Size : 976015360 (930.80 GiB 999.44 GB)
Used Dev Size : 976015360 (930.80 GiB 999.44 GB)
Raid Devices : 2
Total Devices : 3
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sun Feb 23 18:28:45 2020
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Consistency Policy : bitmap
Name : sharon:2
UUID : 98299cb7:9cbe61e9:c8374bcb:3c72d5ca
Events : 704774
Number Major Minor RaidDevice State
0 8 19 0 active sync /dev/sdb3
2 8 3 1 active sync /dev/sda3
3 8 35 1 active sync writemostly /dev/sdc3
--
Aymeric
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: mdadm RAID1 with 3 disks active on 2 disks configuration
2020-02-23 17:38 mdadm RAID1 with 3 disks active on 2 disks configuration Aymeric
@ 2020-02-23 20:40 ` antlists
2020-02-24 9:23 ` Aymeric P.
2020-02-24 9:25 ` Aymeric
0 siblings, 2 replies; 4+ messages in thread
From: antlists @ 2020-02-23 20:40 UTC (permalink / raw)
To: Aymeric, linux-raid
On 23/02/2020 17:38, Aymeric wrote:
> Hello,
>
> I've a system with a RAID1 using two disks (sda + sdb) + 1 spare (sdc).
>
> For some stupid reason (cable) the spare (sdc) became active and sda was
> out the array.
>
> I then added back sda to the RAID1 but now I've RAID1 with three active
> disks and zero spare.
> I don't understand why the spare device didn't switch back as spare
> after sda have been rebuild.
Because rebuilding sda is a lot of work. The sensible option would have
been to leave sdb and sdc active, and left sda as spare.
> I used the following command to add sda to the RAID1:
> # mdadm /dev/md0 --add /dev/sda3
>
>
> What did I do wrong here? And how to fix it? Do I have to set sdc to
> faulty and add it back?
I'd just leave it as a 3-disk raid. But no, if you do want to set it
back to a 2-disk raid don't do a "faulty and re-add" - that'll just make
re-sync it again. Somehow you've got active devices set to 3, so just
set that back to two. If you look on the wiki it covers the scenario of
converting a three-disk raid to two.
The only thing I will add about a 3-disk raid is that if you want to
change it to anything else, you'll have to revert to 2 first, but do
that when you want to change things, leave it at 3 for the moment.
> Thanks!
Cheers,
Wol
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: mdadm RAID1 with 3 disks active on 2 disks configuration
2020-02-23 20:40 ` antlists
@ 2020-02-24 9:23 ` Aymeric P.
2020-02-24 9:25 ` Aymeric
1 sibling, 0 replies; 4+ messages in thread
From: Aymeric P. @ 2020-02-24 9:23 UTC (permalink / raw)
To: antlists, linux-raid
Le 23 février 2020 21:40:44 GMT+01:00, antlists <antlists@youngman.org.uk> a écrit :
>On 23/02/2020 17:38, Aymeric wrote:
>
>Because rebuilding sda is a lot of work. The sensible option would have
>
>been to leave sdb and sdc active, and left sda as spare.
Well, for some reason that didn't happen that way..
>> I used the following command to add sda to the RAID1:
>> # mdadm /dev/md0 --add /dev/sda3
>>
>>
>> What did I do wrong here? And how to fix it? Do I have to set sdc to
>> faulty and add it back?
>
>I'd just leave it as a 3-disk raid. But no, if you do want to set it
>back to a 2-disk raid don't do a "faulty and re-add" - that'll just
>make
>re-sync it again.
I would prefer to revert to sdc as a spare, it's a really a slow disk (5400rpm with a sata1 while others are 7200 at sata3). For a spare disk it's good enough to give me time to get a new disk in case of failure but not for daily.
> Somehow you've got active devices set to 3, so just
>set that back to two. If you look on the wiki it covers the scenario of
>
>converting a three-disk raid to two.
>
>The only thing I will add about a 3-disk raid is that if you want to
>change it to anything else, you'll have to revert to 2 first, but do
>that when you want to change things, leave it at 3 for the moment.
>
So I tried with the --grow option to change the number disk in the array but it doesn't want to change...
# mdadm --grow /dev/md0 --raid-devices=2
mdadm: /dev/md0: no change requested
# mdadm --grow /dev/md0 --raid-devices=3
mdadm: Need 1 spare to avoid degraded array, and only have 0.
Use --force to over-ride this check.
When looking with --examine, sdc3 is marked a replacement device.
# mdadm --examine /dev/sda3 /dev/sdb3 /dev/sdc3|grep 'dev\|Role\|State'
/dev/sda3:
State : clean
Device Role : Active device 1
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdb3:
State : clean
Device Role : Active device 0
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc3:
State : clean
Device Role : Replacement device 1
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
Thanks,
Aymeric
--
Aymeric P.
Phone: +33 685 674 843
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: mdadm RAID1 with 3 disks active on 2 disks configuration
2020-02-23 20:40 ` antlists
2020-02-24 9:23 ` Aymeric P.
@ 2020-02-24 9:25 ` Aymeric
1 sibling, 0 replies; 4+ messages in thread
From: Aymeric @ 2020-02-24 9:25 UTC (permalink / raw)
To: antlists, linux-raid
Le 23 février 2020 21:40:44 GMT+01:00, antlists <antlists@youngman.org.uk> a écrit :
>On 23/02/2020 17:38, Aymeric wrote:
>
>Because rebuilding sda is a lot of work. The sensible option would have
>
>been to leave sdb and sdc active, and left sda as spare.
Well, for some reason that didn't happen that way..
>> I used the following command to add sda to the RAID1:
>> # mdadm /dev/md0 --add /dev/sda3
>>
>>
>> What did I do wrong here? And how to fix it? Do I have to set sdc to
>> faulty and add it back?
>
>I'd just leave it as a 3-disk raid. But no, if you do want to set it
>back to a 2-disk raid don't do a "faulty and re-add" - that'll just
>make
>re-sync it again.
I would prefer to revert to sdc as a spare, it's a really a slow disk (5400rpm with a sata1 while others are 7200 at sata3). For a spare disk it's good enough to give me time to get a new disk in case of failure but not for daily.
> Somehow you've got active devices set to 3, so just
>set that back to two. If you look on the wiki it covers the scenario of
>
>converting a three-disk raid to two.
>
>The only thing I will add about a 3-disk raid is that if you want to
>change it to anything else, you'll have to revert to 2 first, but do
>that when you want to change things, leave it at 3 for the moment.
>
So I tried with the --grow option to change the number disk in the array but it doesn't want to change...
# mdadm --grow /dev/md0 --raid-devices=2
mdadm: /dev/md0: no change requested
# mdadm --grow /dev/md0 --raid-devices=3
mdadm: Need 1 spare to avoid degraded array, and only have 0.
Use --force to over-ride this check.
When looking with --examine, sdc3 is marked a replacement device.
# mdadm --examine /dev/sda3 /dev/sdb3 /dev/sdc3|grep 'dev\|Role\|State'
/dev/sda3:
State : clean
Device Role : Active device 1
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdb3:
State : clean
Device Role : Active device 0
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc3:
State : clean
Device Role : Replacement device 1
Array State : AR ('A' == active, '.' == missing, 'R' == replacing)
Thanks,
Aymeric
--
Aymeric P.
Phone: +33 685 674 843
Aymeric
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-02-23 17:38 mdadm RAID1 with 3 disks active on 2 disks configuration Aymeric
2020-02-23 20:40 ` antlists
2020-02-24 9:23 ` Aymeric P.
2020-02-24 9:25 ` Aymeric
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