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Forum Discussion
FlexRAID expansion (OS 6.7.1)
I've been playing around with how I am going to manage my RN516 and EDA500, looking especially at expansion options once I've disabled XRAID so as to allow for two separate volumes. In so doing, ...
According to this site, Flex-RAID has supported volume expansion since 4.2.15, so it's apparently not a new feature.
Afaik, there are indeed some changes with Flex-RAID since 6.7.0. So horizontal expansion should be more "flexible", as well as more features for the RR4360X.
- I know that prior to 6.7.0, to horizontally expand under Flex-RAID, you need to add as many disks as in the smallest vdev. Let's say you create a 3 HDDs RAID5 array. To horizontally expand it, you need to add another 3 HDDs to trigger the expansion. A second vdev will be created (3 HDDs RAID5 array), and both will be concatenated in the BTRFS volume (in single mode). If you add another 3 HDDs, a third vdev will be created, and so on.
- Based on your description, it seems that this changed, as you were able to expand from a 2 HDDs RAID1 to a 3 HDDs RAID5 while in Flex-RAID.
- Still prior to 6.7.0 (but I think this didn't change), to vertically expand under Flex-RAID, you need to upgrade all the HDDs. It will then extend the existing RAID array in place (instead of creating sub arrays like in X-RAID).
If you want to experiment, you could use a virtual machine and small virtual drives. I guess 20-50GB would work. I have found minor discrepancy on the behavior of X-RAID on virtual and hardware, but that shouldn't be a problem in Flex-RAID mode.
I've never even gotten the virtual machine to work without completely crashing the host Windows machine. Maybe it doesn't like VirtualBox 5.x? I run plenty of other virtual machines, so it's not a general issue.
I'm finding that things work a little different with a NAS and an EDA500 than with a NAS alone, and I doubt the virtual machine has EDA500 emulation.
As for the comment on OS4.2.x supporting FlexRAID expansion, OS4.2.x always had different capabilities than OS6.x. This horizontal expansion capability is definately new in 6.x. jak0lantash says it was added in 6.7.0, and I'll believe that until shown otherwise. I no longer have any systems on anything earlier. But it was definately not there when I was experimenting with a 4200 and an earlier version.
Horizontal expansion capability is there in both mdadm for the RAID volume and BTRFS for the file system,so it's good to see that they have put those together into an easy-to-use option in the GUI for FlexRAID instead of reserving it for XRAID. Maybe we'll get some documentation on it before too long. But I thought I'd play around with it a bit before I move my RN516 + EDA500 into place as my primary system. I've got to figure how I'm going to split my existing shares on the legacy systems over to it, and future expandability is a part of that.
It's good to see that they are adding more functionality to flexraid.
One thing I hope they do is allow people to go from RAID-1 -> JBOD. A lot of people get caught by surprise when they add their first disk, and this option would give them an easy way to undo the automatic behavior.
OK, so here is what I have found so far:
Horizontal expanion works great, as long as the new drive is the same size or larger than the originals. It will offer you the opportunity to add a smaller drive, but it will fail. When I said it just didn't do anything, that was because the drive was in the other chassis (main vs. EDU500). If the new, smaller drive is in the same chassis, it will report a "can't find the drive" error. Clearly a couple glitches in the interface, but nothing that's really critical functionality wise.
No expansion across chassis is possible. The UI will offer you that option, but it will do nothing if you select it.
You can also now add parity to a RAID1 array. Just put in another drive of the same or larger size, and "Add Parity" is now an option. It will convert the RAID1 to an unprotected RAID5 and then begin the sync that makes it protected. Usual sync times apply.
"Add group" is there for creating a JBOD array. There was no offer to add parity, even with a third drive that was of sufficient size.
What I didn't realize initially and led me to test all this is that you can have separate XRAID arrays in the main chassis and the EDU500. I just assumed that would not work and had turned XRAID off before adding drives to the EDA.
Now, the drives are not mounted in any special order as far as the main and EDU chassis are concerned. They get mounted in the order they are sequentially added. In my test situation, sda and adb are the drives I started with in the main, sdc and sdd are in the EDU which I added later, and the drive I added last to the main became sde. So, it is clearly possible that a ReadyNAS could have more than one XRAID array. But managing them could be a nightmare without the physical separation, so I can see why that has not been implemented except in the case of separate chassis. It's obvious which array to add the drive to with the physical separation. If drives 1,2, & 5 were one array and 3 &4 another, which would a drive added to 6 be added to (assuming it was possible for either based on drive size)? And even if it asked, such a jumble of drive positions leaves open a whole host of new possible operator errors removing the wrong drive. But it sure would be nice on a 12-bay system, even if you had to define a "dividing line" before you started.
Thanks for taking the time to explore this - it should be very helpful to people.
Personally I am wondering if they should rethink how XRAID fits in. With OS-6 its really an option for the volume, not a system parameter like it was in OS 4 or OS 5. I think with a little work XRAID could be fully merged into flexraid.
Sandshark wrote:
... Clearly a couple glitches in the interface, but nothing that's really critical functionality wise. ...
No expansion across chassis is possible. The UI will offer you that option, but it will do nothing if you select it.
I agree these don't sound serious. But a lot of users do get tripped up when adding disks - anything Netgear can do to prevent confusion would be good.
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