CentOS - Nov 2020 - Replacing SW RAID-1 with SSD RAID-1

Backup!!!!!!!!

Von meinem iPhone gesendet
> Am 23.11.2020 um 17:10 schrieb centos at niob.at:
> 
> ?On 23/11/2020 16:49, Frank Bures wrote:
>> On 11/23/20 10:46 AM, Simon Matter wrote:
>>>> Hi,
>>>> 
>>>> I want to replace my hard drives based SW RAID-1 with
SSD's.
>>>> 
>>>> What would be the recommended procedure?  Can I just remove one
drive,
>>>> replace with SSD and rebuild, then repeat with the other drive?
>>> 
>>> I suggest to "mdadm --fail" one drive, then "mdadm
--remove" it. After
>>> replacing the drive you can "mdadm --add" it.
>>> 
>>> If you boot from the drives you also have to care for the boot
loader. I
>>> guess this depends on how exactly the system is configured.
>> 
> If you can the new disks while the original 2 disks are still available
then grow, add, wait, fail, remove, shrink. That way you will never loose
redundancy...
> 
> # grow and add new disk
> 
> mdadm --grow -n 3 /dev/mdX -a /dev/...
> 
> # wait for rebuild of the array
> 
> mdadm --wait /dev/mdX
> 
> # fail old disk
> 
> mdadm --fail /dev/sdY
> 
> # remove old disk
> 
> mdadm /dev/mdX  --remove /dev/sdY
> 
> # add second disk
> 
> mdadm /dev/mdX --add /dev/...
> 
> # wait
> 
> mdadm --wait /dev/mdX
> 
> # fail and remove old disk
> 
> mdadm --fail /dev/sdZ
> 
> mdadm /dev/mdX  --remove /dev/sdZ
> 
> # shrink
> 
> mdadm  --grow -n 2 /dev/mdX
> 
> 
> 
> 
> peter
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On 23/11/2020 17:16, Ralf Prengel wrote:
> Backup!!!!!!!!
>
> Von meinem iPhone gesendet
You do have a recent backup available anyway, haven't you? That is: Even 
without planning to replace disks. And testing such strategies/sequences 
using loopback devices is definitely a good idea to get used to the 
machinery...

On a side note: I have had a fair number of drives die on me during 
RAID-rebuild so I would try to avoid (if at all possible) to 
deliberately reduce redundancy just for a drive swap. I have never had a 
problem (yet) due to a problem with the RAID-1 kernel code itself. And: 
If you have to change a disk because it already has issues it may be 
dangerous to do a backup - especially if you do a file based backups - 
because the random access pattern may make things worse. Been there, 
done that...

peter
>> Am 23.11.2020 um 17:10 schrieb centos at niob.at:
>>
>> ?On 23/11/2020 16:49, Frank Bures wrote:
>>> On 11/23/20 10:46 AM, Simon Matter wrote:
>>>>> Hi,
>>>>>
>>>>> I want to replace my hard drives based SW RAID-1 with
SSD's.
>>>>>
>>>>> What would be the recommended procedure?  Can I just remove
one drive,
>>>>> replace with SSD and rebuild, then repeat with the other
drive?
>>>> I suggest to "mdadm --fail" one drive, then
"mdadm --remove" it. After
>>>> replacing the drive you can "mdadm --add" it.
>>>>
>>>> If you boot from the drives you also have to care for the boot
loader. I
>>>> guess this depends on how exactly the system is configured.
>> If you can the new disks while the original 2 disks are still available
then grow, add, wait, fail, remove, shrink. That way you will never loose
redundancy...
>>
>> # grow and add new disk
>>
>> mdadm --grow -n 3 /dev/mdX -a /dev/...
>>
>> # wait for rebuild of the array
>>
>> mdadm --wait /dev/mdX
>>
>> # fail old disk
>>
>> mdadm --fail /dev/sdY
>>
>> # remove old disk
>>
>> mdadm /dev/mdX  --remove /dev/sdY
>>
>> # add second disk
>>
>> mdadm /dev/mdX --add /dev/...
>>
>> # wait
>>
>> mdadm --wait /dev/mdX
>>
>> # fail and remove old disk
>>
>> mdadm --fail /dev/sdZ
>>
>> mdadm /dev/mdX  --remove /dev/sdZ
>>
>> # shrink
>>
>> mdadm  --grow -n 2 /dev/mdX
>>
>>