Is there a way to grow raid from a raid 1 to a raid 5 system without loosing data?
Possible....risky yes. I will describe this briefly as you can find many in other websites
Proceed to mark the raid1 as degraded by removing one disk.
Erase the superblock and fs signature of the removed disk.
Created a degraded raid5 with only two disks, the new one and the one you just removed. Create the fs on the new md array, mount.
Rsync the contents of the raid1 to raid5.
Delete the raid1, erase the single disk superblock and filesystem signature, then add that disk to the raid5 and wait for it to sync.
I would strongly encourage that you better have backup before doing this.
With a big external hard drive or another mirror server. Also make sure you select the important stuff.
Hello,
I recently had to grow a RAID 1 to 5 on a Proxmox, I used this guides to achieve it :
https://raid.wiki.kernel.org/i…ror_raid_to_a_parity_raid
https://www.howtoforge.com/how…artitions-shrink-and-grow (for lvm)
But I don't disagree @subzero79 at all : you SHOULD backup your data before trying this grow =)
Hi Guys,
just curiosity, I've been using OMV for a while only with a single HDD, and right now I'm just learning about RAID systems in order to add extra space in the future to my NAS.
I already saw the posibility of growing from 1 to 5 as commented here
Hello,
I recently had to grow a RAID 1 to 5 on a Proxmox, I used this guides to achieve it :
https://raid.wiki.kernel.org/i…ror_raid_to_a_parity_raid
https://www.howtoforge.com/how…artitions-shrink-and-grow (for lvm)
But I don't disagree @subzero79 at all : you SHOULD backup your data before trying this grow =)
but recently I also saw this blog entry (sorry is in spanish)
http://lopezivan.blogspot.com/…raid-1-un-raid-5-sin.html
where they use instead of the --grow simply the --create in this way:
mdadm --create /dev/md3 --level=5 --raid-devices=2 /dev/sdf1 /dev/sdg1to create a degradaded level 5 RAID but using the two existing mirrors instead of creating an empty degraded RAID 5 and copying the data from the remaining disk of the mirror.
Just for curiosity, is one of the two ways safer to use?
thx!
just curiosity, I've been using OMV for a while only with a single HDD, and right now I'm just learning about RAID systems in order to add extra space in the future to my NAS.
Why Raid? I have just move from a Raid5 to using mergerfs and snapraid, with this only the parity drive on snapraid must be the largest drive, in essence you can use drives of various sizes, unlike an mdadm raid.
is one of the two ways safer to use?
Save? How large are your disks? Are you aware that you're affected by the classical parity RAID write hole unless you specify a log device when creating a RAID5? Are you aware that with single redundancy (RAID5) once a single disk fails you're left with no redundancy at all and that a rebuild with large disks can take days to weeks?
Why Raid? I have just move from a Raid5 to using mergerfs and snapraid, with this only the parity drive on snapraid must be the largest drive, in essence you can use drives of various sizes, unlike an mdadm raid.
Well, as I said, is just curiosity right now. I've been thinking about raid, in order to see all the drives as one single filesystem, therefore I was thinking about using just a simple raid0 or so, but as I said I'm just learning right now since never used RAID before.
Save? How large are your disks? Are you aware that you're affected by the classical parity RAID write hole unless you specify a log device when creating a RAID5? Are you aware that with single redundancy (RAID5) once a single disk fails you're left with no redundancy at all and that a rebuild with large disks can take days to weeks?
The question was just for curiosity, since in my case I'm not interested on redundancy (at least for now) since all the data I'm storing in the NAS is just multi-media, and the important stuff I've it backed up in several cloud services. The thing is, I'm just reading about different level's of RAID in order to have the more info possible, and these two methods to migrate from one level to another attracted my attention.
Therefore, there are no disks hahaha (well just one 4tb WD), and yes, I already knew the risks, and that the rebuild can take a lot of time.
I'm not interested on redundancy (at least for now)
Then better skip RAID. Today most probably what @geaves suggested is the best idea. You could also do a multi device btrfs setup but currently with OMV4 btrfs integration is a bit lacking. I hope this changes with OMV5 but there's no release date yet and everything still alpha...
Well, as I said, is just curiosity right now. I've been thinking about raid
We have a saying in the UK "curiosity killed the cat" 
TBH, for home use Raid is not a good idea and a total waste of drive space and usage + if it goes wrong it usually goes wrong big time BTDTGTTS 
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