RAID 6 to RAID 5?

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Stewart
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I have a QNAP NAS in the office. It has 4 hard disks and runs RAID 6.

The thing is, I don't know why I originally set it up to run RAID 6. I'm only getting 50% of the total disk capacity as available space, whereas if it were running RAID 5 I would get 75%. I know that RAID 6 can withstand two simultaneous disk failures whereas RAID 5 can only withstand one disk failure, but that's a risk I'm prepared to take. Everything is backed up every night and if a disk fails I can get a replacement within 24 hours.

So I think I'd like to downgrade the RAID level from 6 to 5. That's not officially supported by QNAP - in other words, their RAID migration tool won't do it. Can anyone suggest how I might do it myself, other than backing up the data, formatting the disks, rebuilding the RAID, and restoring all the data?
 
Don't think it can be done..... This link says No

Unless you have 4x spare disk slots/bays and build an additional RAID 5 volume
 
Personally I would stick with Raid 6 and if you need more space increase the disk sizes.
I use raid 6 known more as ADG as it stores all my business stuff.
bear in mind if a disk fails in raid 5 you are then putting a lot more stress on your existing disks and if the unfortunate happens you are then stuffed.
 
You can't change raid levels on the fly.

Other bad things about raid5 are the rebuild times and the stress it places on other disks which could result in a secondary failure.

That said I run 5 on my qnap. But it's backed up and I have alternative means of working during a failure.
 
Don't think it can be done..... This link says No
Yes, thanks, I'd seen that. Strictly speaking, that link says it's not supported by the QNAP migration utility, which isn't quite the same thing.

Whereas this link, also from the QNAP support forum, suggests that it might be possible to do it on the fly..... which is why I was asking.
 
Personally I would stick with Raid 6 and if you need more space increase the disk sizes.
I get where you're coming from. But how can I do that? Can I take out a single 2TB disk and replace it with, say, a 4TB disk, on the fly?
 
I get where you're coming from. But how can I do that? Can I take out a single 2TB disk and replace it with, say, a 4TB disk, on the fly?

Yes you will need to check with QNAP but that's it.
You can replace each disk in sequence then when they are all replaced you should be able to do an array expansion.
 
Yes you will need to check with QNAP but that's it.
You can replace each disk in sequence then when they are all replaced you should be able to do an array expansion.

Just to clarify (I'm assuming QNAP behavior is the same as Synology in this case), you need to replace 1 disk, wait for the rebuild, then replace the 2md disk, wait for rebuild, etc.
 
Just to clarify (I'm assuming QNAP behavior is the same as Synology in this case), you need to replace 1 disk, wait for the rebuild, then replace the 2md disk, wait for rebuild, etc.

oh yes for sure you will need to use whatever QNAP software it has to make sure the array is back to 100% after each disk rebuilds.
that could take 24 hours / disk.
there might be a setting on the QNAP for rebuild priority which needs to be set to high.
 
Yes you will need to check with QNAP but that's it.
You can replace each disk in sequence then when they are all replaced you should be able to do an array expansion.
Just to clarify (I'm assuming QNAP behavior is the same as Synology in this case), you need to replace 1 disk, wait for the rebuild, then replace the 2md disk, wait for rebuild, etc.
oh yes for sure you will need to use whatever QNAP software it has to make sure the array is back to 100% after each disk rebuilds.
that could take 24 hours / disk.
there might be a setting on the QNAP for rebuild priority which needs to be set to high.
Thanks guys. Couldn't be clearer. I might give it a go.
 
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