SHR2 to SHR

[rickym]

This has probably been covered on the forum but my search didn't find the answer. Can I convert from shr2 to shr without totally re-doing my server. I don't have a way right now to remove everything from my server to do a re-install synology at this time. Hope that makes sense.

[IG-88]

as no one answered this by now i can try to give my best here

shr is a combination of a underlying mdadm and above lvm2 and is usually used with "asymetric" disk pairing (different sizes)

afair synology does not support it and when trying to do it manually it would be kind of complicated

in theory the size of the lvm file system would still be the same when just reducing the redundancy from 2 to 1

the problem is that your lvm consists of numerous mdadm arrays and every one of them would need to be reduced in redundancy

so there is no universal way, its something you would need to understand and adapt it to your situation

a two disk redundancy is a raid6 and a raid1 with 3 disks

the result would be raid5 and raid1 with 2 disks

it depends on your disks how your system is configured in terms of mdadm

 

you could have a peek here to see how its done on mdam level

https://www.linuxquestions.org/questions/linux-general-1/how-to-migrate-from-raid-6-to-raid-5-using-mdadm-and-lvm-939508/

i guess its pretty much the same for raid one with 3 disks, only its not really change in raid level, its just permanently removing one disk from the raid, so its kind of easier the raid6->raid5

 

you should have a backup because its easy to mess up things

 

in most cases people weighting the time to invest, what can go wrong and decide for the way they can safely use and most often that would end in backup (you would need that anyway) and then just delete the array and do a  restore, might take hour to days to restore from backup  but when its just personal use its just a little inconvenience compared with hours of reading, maybe trying that on a virtual system before doing it on the real system

compared to nearly no extra knowledge and just doing a backup/restore, and just the time invest for using the backup software its way more cumbersome to do it  the technically most elegant way by reducing the raid level and only very few people will choose that way when never used mdadm/lvm  before

 

edit: maybe google for "mdadm migrate raid 6 to raid 5" to find more information

 

Edited December 5, 2020 by IG-88