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Forum Discussion
how to remove a hard disk clean from a raid (RN 314, using SSH)
Hey there, i would like to remove a specific hard drive from the volume cleanly. First, is my plan very risky, even possible at all in this way? Afaik i would first use: btrfs device ...
Equinox1 wrote:
...However, I wouldn't want to be in your testing team. Nevertheless, it would be a diferenciating feature in the current NAS market.
I don't work for Netgear, but I wouldn't want to be on the testing team either. There is one common case, where it is simple. That's when new users insert their second disk, and are shocked that they don't get more space. Downgrading RAID-1 back to jbod would allow an easy recovery.
This request is already posted on the ideas exchange, if you are interested in it you could vote for it: https://community.netgear.com/t5/Idea-Exchange-for-ReadyNAS/Switching-disc-configuration-to-user-FEWER-drives-or-FEWER-but/idi-p/988384
It's worth looking at all of those ideas, and voting for all the ones you think you'd use.
I have succesfully 'downgraded' a RAID 6 volume on OS 6.3.5 to RAID 5, once (in order to use one of the disks in another system).
As far as my very limited knowledge goes, hou have to disable xraid first (at least I did). When the RAID 6 volume is in flexraid mode, I could change stuff via the command line as long as the volume size didn't change. (mdadm RAID 6 to mdadm RAID 5 keeps the same BTRFS volume size).
After being done, change back to xraid and a new disk will expand the volume (confirmed).
Of course, ymmv and no guarantees whatoever.
If you wanted to reduce the volume capacity, that is where there would certainly be much higher risk. As you'd be relying on a number of things working well and if just one of them doesn't then there could be big issues.
We know backups are important, but there would be users who would not update their backup (if they even have one) before doing such an operation even if we provide a number of warnings to do so.
mdgm wrote:
If you wanted to reduce the volume capacity, that is where there would certainly be much higher risk. As you'd be relying on a number of things working well and if just one of them doesn't then there could be big issues.
A middle ground could be a documented "at your own risk" ssh procedure.
Also, even if volume reduction can't be done, downgrading raid redundancy (raid1->jbod, raid 6->raid 5) would give users more options when their NAS runs out of capacity.
I agree.
The 'key' here is that the most common scenario is not shrinking the capacity 'per se' but reducing the number of units it relies on.
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