FlexRAID expansion (OS 6.7.1)

Question

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, I discovered a minor bug. I created two volumes, one RAID1 with two 2TB drives in the main chassis and one with 2 1TB's in the EDA500. Once that was all set up and sync'ed, I inserted another 1TB into the EDA500. The options presented to me were for the array of 2TB's and included "Expand" or "Cancel". "Add Parity" and "Add Group" were not available. But a 1TB drive cannot be used to expand an array of 2TB drives. If I clicked on it, nothing happened. And while nothing should happen except maybe an error message, it could be confusing to some that the option was available at all.

It was not inherently clear that I had to click on the volume information for the other volume to see the options for it (though I suppose most would ultimately try it). Clicking on Expand did work for that volume, and it' still re-syncing but looks like it should work, converting to RAID5.

This is on OS6.7.1, but I seriously doubt it's on the list of fixes for versions up to 6.7.4.

Note that this ability is contrary to what is in ReadyNAS-Volume-Expansion, which states "With Flex-RAID formatting, if you want to add disks to expand your storage capacity, you must back up the data to another system, add a disk, reformat the RAID volume, and restore the data to the new RAID volume." and also "You can added (sic) disks physically using an EDA500 Expansion chassis. However this will be a separate Volume. X-RAID is not supported across different chassis." I have not tried expanding XRAID across chasses, but it is certainly showing me I can expand FlexRAID across them.

Perhaps these capabilities are new, but they are very welcome and Netgear should make sure potential buyers are aware of this capability.

Unless somebody can point me to an accurate description of current expansion capabililities, I will continue to do some experiments and see what happens.

Still to try: Expanding an array with a larger drive (or two). Replacing a bad drive with a larger drive (I've seen some indication this won't work). Expanding an array of mixed drives that was created under XRAID and then changed to FlexRAID (no idea what to expect). Each test takes a long time to sync (which is why I'm using smallish drives for the experiments) and I may need to factory default between some tests to be sure I'm starting "clean", so it may take some time to do all this. While I don't plan to expand an array across the chassis boundry, I'll see about testing Expanding FlexRAID across chassis boundry (shown available, but not yet tested) and expanding XRAID across the chassis boundry.

jak0lantash · Answer

Afaik, there are indeed some changes with Flex-RAID since 6.7.0.&nbsp;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).&nbsp;

&nbsp;
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.

Sandshark · Answer

OK, so here is what I have found so far:&nbsp;Horizontal expanion works great, as long as the new drive is the same size or larger than the originals.&nbsp; It will offer you the opportunity to add a smaller drive, but it will fail.&nbsp; When I said it just didn't do anything, that was because the drive was in the other chassis (main vs. EDU500).&nbsp; If the new, smaller drive is in the same chassis, it will report a "can't find the drive" error.&nbsp; Clearly a couple glitches in the interface, but nothing that's really critical functionality wise.&nbsp;No expansion across chassis is possible.&nbsp; The UI will offer you that option, but it will do nothing if you select it.&nbsp;You can also now add parity to a RAID1 array.&nbsp; Just put in another drive of the same or larger size, and "Add Parity" is now an option.&nbsp; It will convert the RAID1 to an unprotected RAID5 and then begin the sync that makes it protected.&nbsp; Usual sync times apply.&nbsp;"Add group" is there for creating a JBOD array.&nbsp; There was no offer to add parity, even with a third drive that was of sufficient size.&nbsp;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.&nbsp; I just assumed that would not work and had turned XRAID off before adding drives to the EDA.&nbsp;Now, the drives are not mounted in any special order as far as the main and EDU chassis are concerned.&nbsp; They get mounted&nbsp;in the order&nbsp;they are sequentially added.&nbsp; 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.&nbsp; So, it is clearly possible that a ReadyNAS could have more than one XRAID array.&nbsp; 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.&nbsp; It's obvious which array to add the drive to with the physical separation.&nbsp; If drives 1,2,&nbsp;&amp; 5 were one array and 3 &amp;4 another, which would a drive added to 6 be added to (assuming it was possible for either based on drive size)?&nbsp; 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.&nbsp; But it sure would be nice on a 12-bay system, even if you had to define a "dividing line" before you started.

mdgm-ntgr · Answer

Having one volume spanned across two chassis is risky. If the eSATA cable is disconnected "accidentally" it could cause a lot of problems.

ctechs · Answer

According to this site, Flex-RAID has supported volume expansion since 4.2.15, so it's apparently not a new feature.&nbsp;http://home.bott.ca/webserver/?p=550

Sandshark · Answer

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.

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FlexRAID expansion (OS 6.7.1)

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