Transferring RAID5 array – comments please

[helen314]

I am in a process of temporary transferring RAID5 array – from USB stick to USB drive.
I have successfully added copy of current array /dev/sdkx partitions as /dev/sdex
using mdadm –add ….



I have experienced an error advising to “backup critical ...”
Unfortunately my barely limping Ubuntu 16.04.7 froze so I did not get the actual copy of the message.


After reboot I checked the array :







root@f-SATA:/home/f# mdadm --detail /dev/md42

/dev/md42:
Version : 1.2
Creation Time : Thu Oct 15 09:50:58 2020
Raid Level : raid5
Array Size : 5564416 (5.31 GiB 5.70 GB)
Used Dev Size : 2782208 (2.65 GiB 2.85 GB)
Raid Devices : 8
Total Devices : 8
Persistence : Superblock is persistent



Update Time : Fri Oct 30 13:58:49 2020
State : clean, reshaping
Active Devices : 8
Working Devices : 8
Failed Devices : 0
Spare Devices : 0



Layout : left-symmetricState : clean, reshaping
Chunk Size : 512K



Reshape Status : 32% complete
Delta Devices : 5, (3->8)



Name : a-SATA:42
UUID : fbe4babd:b3c28449:66d4881d:46391ff4
Events : 286



Number Major Minor RaidDevice State
0 8 161 0 active sync /dev/sdk1
1 8 162 1 active sync /dev/sdk2
4 8 164 2 active sync /dev/sdk4
8 259 6 3 active sync /dev/sde22
7 259 5 4 active sync /dev/sde21
6 259 4 5 active sync /dev/sde20
3 8 163 6 active sync /dev/sdk3
5 8 165 7 active sync /dev/sdk5







root@f-SATA:/home/f#



Please note its “state” :
State : clean, reshaping
It is going to take some time.



Can I make the following assumptions ?



1. After “reshaping “ is done – can I physically remove sdk ?

It is USB memory stick. But it probably will remain as a (what type? inactive ?? ) of device in md42 array .
I can live with that.

2. Would it be prudent to “remove” sdkx using mdadm software instead?.

It should not take much of real time is my best guess.

[helen314]

Update

As an experiment, I did , after copying the array contents to another , plain partition, physically REMOVED the USB drive.
After reboot, reinserted th USB stick.
Did not expect the array to be functional, but this got me puzzled.
At one point the entire array was gone.

Here is a series of commands of strange responses and still not functioning array.




f@f-SATA:~$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md2 : active raid5 sde11[3] sde17[4](S) sde4[0] sde5[1] sde18[5](S)
204668928 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]

md42 : inactive sde21[7](S) sde22[8](S) sde20[6](S) sdk2[1](S) sdk4[4](S) sdk5[5](S) sdk3[3](S) sdk1[0](S)
22798336 blocks super 1.2

md20 : active raid5 sdf22[3] sdf20[0] sdf21[1]
204668928 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]

md3 : active raid5 sdf12[0] sdf13[1] sdf14[3]
204668928 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]

md1 : active raid5 sde9[3] sde19[5] sdd9[4]
204668928 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]

md0 : inactive sda3[0](S) sdc4[1](S)
204668928 blocks super 1.2

unused devices: <none>
f@f-SATA:~$ sudo mdadm --run /dev/md42
[sudo] password for f:
mdadm: failed to start array /dev/md/42: Input/output error

f@f-SATA:~$ sudo mdadm --assemble --force /dev/md42
mdadm: Found some drive for an array that is already active: /dev/md/42
mdadm: giving up.

f@f-SATA:~$ sudo mdadm --detail /dev/md42
/dev/md42:
Version : 1.2
Creation Time : Thu Oct 15 09:50:58 2020
Raid Level : raid5
Used Dev Size : 2782208 (2.65 GiB 2.85 GB)
Raid Devices : 8
Total Devices : 6
Persistence : Superblock is persistent

Update Time : Fri Oct 30 18:44:01 2020
State : active, FAILED, Not Started
Active Devices : 6
Working Devices : 6
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 512K

Name : a-SATA:42
UUID : fbe4babd:b3c28449:66d4881d:46391ff4
Events : 465

Number Major Minor RaidDevice State
0 8 161 0 active sync /dev/sdk1
1 8 162 1 active sync /dev/sdk2
4 8 164 2 active sync /dev/sdk4
8 259 6 3 active sync /dev/sde22
7 259 5 4 active sync /dev/sde21
6 259 4 5 active sync /dev/sde20
12 0 0 12 removed this is /dev/sdk3 what "removed it"?
14 0 0 14 removed this is /dev/sdk5
f@f-SATA:~$



So I a have " State : active, FAILED, Not Started" which is " mdadm: Found some drive for an array that is already active: /dev/md/42"
and "mdadm: giving up. "

Any suggestion what to TRY next ?

[helen314]

YAA
Yet another addendum







f@f-SATA://etc/mdadm$ sudo mdadm --assemble --scan
mdadm: ignoring /dev/sde22 as it reports /dev/sdk4 as failed
mdadm: ignoring /dev/sde21 as it reports /dev/sdk4 as failed
mdadm: ignoring /dev/sde20 as it reports /dev/sdk4 as failed
mdadm: /dev/md/42 assembled from 3 drives - not enough to start the array.
mdadm: /dev/md/00 is already in use.
f@f-SATA://etc/mdadm$





Array is assembled but it was initially created with 8 members.
Question:
Is it possible to change # of devices in an array after it has been created?

Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0