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Re: feature request - tool for offline expansion

alexofindy
Aspirant

feature request - tool for offline expansion

I have a readynas ultra plus with four 3 TB drives, configured as X-RAID2. I cannot further expand the volume because I will hit the 8 TB lifetime expansion limit.

This is because when I first configured the system, I installed three drives, one at a time. This was in accordance with the written instructions in the Readynas documentation. Unfortunately, the documentation was wrong; it would have been far better if I installed the three drives all at once, and then reinitialized (factory defaulted). This would have avoided my current problem.

Though I do back up my critical data on to both a USB drive and another (smaller) readynas, I have no system with enough capacity on which I can back up all my data. Thus, I cannot easily do a factory default.

I've read the the 8TB limit can be bypassed by doing an offline expansion. If this is true, I would like to see you folks provide a tool or instructions so that and end user such as myself can do the expansion.

Thanks!
Message 1 of 10
StephenB
Guru

Re: feature request - tool for offline expansion

Getting the offline expansion procedure documented would be helpful, I'd like to see that also.

There is of course a risk doing expansion w/o a backup. Though painful, you could possibly temporarily store some of the data onto the new drive (putting it temporarily in a PC). If that is enough to hold the unbacked up folders, you could then do the default.
Message 2 of 10
PapaBear1
Guide

Re: feature request - tool for offline expansion

alexofindy - you state that you have an ultra plus with four 3TB drives and lament the inability to expand further without a factory reset. Do you have an Ultra 6 Plus? If it is an Ultra 4 Plus, you cannot expand vertically unless you go to 4TB drives and there are no 4TB drives currently on the official HCL although some have successfully used them.

StephenB has a very good point in that any time you do a volume expansion or even an firmware update although normally there is not problem there is still that small change of something going wrong. While it is good that you have the critical data backed up (hopefully one copy on the USB drive and one copy on the other NAS) what about the data that is not backed up at all? Is it video and music that you have the original source, then while it may be a PITA to recreate, it can be done, but if you have not other backup, is it that unimportant? I can relate, for it took me years to get into the position where I backed up my data NAS to NAS overnight, and I certainly would not want to go back.

Unless you are running out of space, you may want to review your backup strategy rather than expand at this point.

The on line expansion limit of 8TB above the original volume size and 16TB total (yes there is another one) is not a situation in the ReadyNAS alone, but in the Linux kernal so others are subject to it as well. The primary reason with starting with one drive and then adding the others one at a time is that way each individual drive is tested, so if it hangs or has a problem, you can readily identify the problem drive. Starting with them all at once works as long as there is not a problem with any of the drives as then if it detects a bad drive and halts, which drive is it?

Basically the recommendation now is to add them one at a time, but once they have all been tested and accepted and added to the volume, to do a factory default before adding data. Of course this will not help you.
Message 3 of 10
alexofindy
Aspirant

Re: feature request - tool for offline expansion

Thanks very much, PapaBear and StephenB. The data I haven't backed up is stuff that can be replaced, but it would be time consuming (nothing more) to do so.

The data I need is backed up (rsync running on a nightly schedule) to an NV+ configured as flextraid, mirror (Raid 1), and it uses 4K block size, so I can mount the disks on a Linux PC with little effort. And there's a USB drive backup of the same data. And the really, really important data also goes on bluray disks which I store offsite.

So, when I ask for expansion tools, it's for convenience. But convenience counts.

Do either of you happen to know the specific answer to my question - are there Linux tools that will perform an offline expansion that exceeds the 8TB limit?

And I do stand on my original gripe with Readynas: they should make this issue clear in their documentation. It is not a new thing, though it only became an issue with affordable 6-bay units (I do have a 6 bay Ultra 6+) and 3 TB drives.
Message 4 of 10
StephenB
Guru

Re: feature request - tool for offline expansion

There is an offline procedure expansion here: https://www.readynas.com/forum/viewtopi ... 6&p=356612

Note this will not overcome the 16 TB size limitation (as explained by chirpa in the linked thread), however it can overcome the 8 TB growth limit. I haven't tried it.
Message 5 of 10
alexofindy
Aspirant

Re: feature request - tool for offline expansion

Yes, that is what I want.

I have previously seen this guide, but I was put off by Chirpa's comment that expanding using this trick was destined to ultimately fail because the tools were not 64bit clean. I don't understand the implications of Chirpa's comment. Chirpa seemed to be talking about the 16 TB limit, which isn't my issue; I don't know if his warning applies to using the method to expand beyond 8 TB over the initial filesystem size, which is my issue.

I realize that expansion is always a bit dangerous, so backups are essential for critical data. But I don't want to waste time doing something that is certain to fail.

Bottom line: netgear's documentation recommended adding disks one at a time, and didn't mention the 8 TB expansion issue. Big mistake, to myself and others on this forum. I would like to see the company set things right by testing the method in the post you cite, and letting us know if works, albeit with risks. If it does, I think they should provide a user friendly add-on to facilitate the process (though I myself could probably handle the command line approach).
Message 6 of 10
chirpa
Luminary

Re: feature request - tool for offline expansion

My notes were for expanding beyond 16TB. If you are expanding but still below 16TB, it should be fairly safe.

The lifetime expansion of 8+TB is something someone from NTGR will need to comment on.
Message 7 of 10
StephenB
Guru

Re: feature request - tool for offline expansion

If you use a block size of 4K, then 32 bit block addressing will overflow at 16 TiB (2**32 * 4096 = 16 TiB). So when expanding to a volume size sizes above that, all the block addresses are extended to 64 bit. Chirpa is saying that resize2fs doesn't work with 64 bit block addresses.
Message 8 of 10
chirpa
Luminary

Re: feature request - tool for offline expansion

For crossing that boundary yes. If you start fresh over 16TB thats fine. But crossing that threshold, on an older version of ext3/4 file system, there will be issues.

I think it was for similar reasons that the snapshot resize has been disabled for so many releases.
Message 9 of 10
alexofindy
Aspirant

Re: feature request - tool for offline expansion

Thanks, Chirpa and StephenB.

I hope someone from Netgear will read this and respond regarding the 8TB limit.

Netgear is selling 6 bay units, and with 3TB drives (and now 4 TB) the norm, these limits need to be addressed. And if there are workarounds for the 8TB limit through offline expansion, these options should be made available to customers.

I appreciate everyone's help!
Message 10 of 10
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