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Moving an EDA500 Expansion Chassis to a New NAS

In the course of upgrading my RN716 from 6.9.5 to 6.10.0 the 716 failed completely boot (several times). I solved that issue through the boot menu and an OS reinstall . . .

 

BUT, and this is my real question: How do you mount an EDA500 with an existing volume on another ReadyNAS, in my case an RN314???

 

Details:

 

I use an EDA500 expansion chassis to backup everything on the 716 (and I also backup to the clouds). So before I tried anything to solve the problem with the 716 I tried to connect the EDA500 to my older RN314 which has three 2TB drives and data. After powering up the 314 could see that there was an expansion chassis connected but would not recognize (mount?) the volume on the EDA. It said something like (sorry I forgot exactly what) the disks were inactive(?).

 

The documentation talks about exporting a volume so that it can be mounted on another NAS but this was not possible given the 716 was inoperable.

 

So what is the process for connecting an expansion chassis to another RN and being able to read/recover the files on it?

 

Thanks

 

 

RN716X|ReadyNAS 716X Chassis; RN314 ReadyNAS, EDA500

Model: RN716X|ReadyNAS 716X Chassis (Diskless)
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Luminary

Re: Moving an EDA500 Expansion Chassis to a New NAS

So many thanks to both StephanB and Sandshark!

 

The short answer to the problem of trying to recover a volume on an EDA500 when the host NAS has crashed (so the volume on the EDA cannot be EXPORTED) is that it is very difficult. And therefore it is not wise to use, as I did, an expansion chassis to backup the volume on the host NAS . . .   A second NAS (using rsync) or USB or eSATA drives are reliable solutions (with rsync being 2 1/2 times faster than to drives attached to the NAS).

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Re: Moving an EDA500 Expansion Chassis to a New NAS

Export the volume on the old NAS.  Power down and remove the EDA500.  Attach to new NAS with power on.  Turn power on and the new NAS will see and import the EDA500 volume.

 

While I have successfully done this more than once, a full backup of the EDA500 contents is always good insurance before doing this.

 

One caveat:  Neither the volume name nor the share (aka subvolume) names on the EDA500 can match any on the new NAS.  You can, of course, rename shares before the export.  I have not yet successfully figured out how to safely rename the volume.

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Re: Moving an EDA500 Expansion Chassis to a New NAS

Sandshark, thank you. Yes, that should work - though I've never tried it - as long as you can successfully export the volume.

 

BUT if the NAS that has the EDA500 attached crashes - as my 716 essentially did - I could not export the volume.

 

So my question, sorry it was not clear, is how do you mount the volume on the EDA500 on another NAS when the NAS the expansion unit is normally connected to crashes and the volume on that expansion unit has not been exported ahead of time???

 

 

TIA

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Re: Moving an EDA500 Expansion Chassis to a New NAS

I'm not sure what the "export" function does, so I wasn't sure what would happen if you try to import a non-exported drive to another NAS.  Or, for that matter, back to the same NAS after doing a factory default with the EDA disconnected.

 

When you export and import, the permissions are changed, since the user and group UID/GID may not be the same on the new NAS.  But I don't know how the export is part of that process.  And the UUID of the original and receiving NAS are different, which could cause all kinds of issues.

 

While it's a bit different, I just ran an experiment, moving a non-exported secondary volume (but not in a separate chassis) from one NAS to another. This failed.  The volume was not accessable, being labeled an unused volume.

 

So, I went to SSH and tried to mount it, and it was not shown as an MDADM volume.  So, I did an mdadm  --assemble  --scan, which created three new md_ devices, one from the OS volume partitions (partition 1) of the added drives, one from the swap volume partitions (partition 2, which the EDA500 should have as free space), and the one I was looking for from the data volume partitions (partition 3).  cat /proc/mdstat let me know that the one I was looking for, consisting of the third partition of the drives, was md126, so I did a mount  /dev/md126  /mnt to mount it to the /mnt directory that's present for just such recovery and investigative occasions.  That made the contents of the volume accessible from SSH, but nothing I tried could make the GUI identify the volume and make it accessible or make the NAS automatically re-assemble the volume on a re-boot.  So, this can serve as a way of recovering data from an "orphaned" volume via SSH (copying to another volume, USB device, or even mounted external device), but not to move a volume from one NAS to another.  It could get messier if the data volume consisted of more than one RAID layer.

 

Will an EDA500 volume behave the same, since it's in a separate chassis?  I don't know.  If you have a backup, I'd say just try it and reformat and recover from backup if it doesn't.  If you don't, and none of the Netgear folks chime in to say where I went wrong in my attempt, you're likely going to need paid Netgear support.

 

BTW, it appears nothng bad happened to the moved volume itself.  All went fine when I moved it back to the original NAS.  But if I had no backup, I don't think I'd trust that to always be the case and try any of this to see if the EDA volume behaved any differently.

 

Note, too, that I have previously created a volume "behind the scenes" with SSH and the GUI does recognize it once mounted, and does so permanently with an entry to etc/fstab.  So, there is definately something different in the movement vs. creation of a volume.  I suspect a lot of this has to do with the UUID of the moved volume not matching the one on the receiving NAS, which would not be the case on a created volume.  The UUID would also be different when re-connecting to a NAS that had been factory defaulted, so I expect there would be similar issues trying that.

 

How the "export" function  sets things up so it's not an issue, I have no idea.  So, I don't know if you can do that manually on another NAS or not.

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Re: Moving an EDA500 Expansion Chassis to a New NAS

Thank you again Sandshark! 

 

I am hoping that MDGM or StephanB or someone from NetGear will chime in . . . 

 

But at this point it looks like my strategy of using the EDA500 as a set of backup drives for the data on my 716 likely is flawed (darn! I got it for a nice price when it was officially discontinued). At least for the majority of us who are not familiar and skilled with UNIX shell commands as you are. Too bad that it appears not to behave as a single eSATA drive would behave.

 

The documentation (not so clearly) says that the "export" function for a volume unmounts the volume. 

 

What seems to be missing is an easy way to mount or "import" a volume, and in the case of disaster recovery force a volume from a crashed NAS to mount on another NAS.

 

Lets see what the Netgear folks say. TIA folks!

 

 

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Re: Moving an EDA500 Expansion Chassis to a New NAS

The import is "automatic", but appears to only work properly with an exported volume.  So, the export must be doing something to the volume more than just dismounting it.  Whether that "something" can be done on another system, I can't determine, since I don't know what the "something" is.

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Re: Moving an EDA500 Expansion Chassis to a New NAS


@hmuessig wrote:

 

I am hoping that MDGM or StephanB or someone from NetGear will chime in . . . 


I've never owned a EDA500, so @Sandshark has a lot more experience with this than I have.  

 

It should be possible to mount it's volume from the cli (even if it doesn't show up in the web ui).

 


@hmuessig wrote:

The documentation (not so clearly) says that the "export" function for a volume unmounts the volume. 

 

What seems to be missing is an easy way to mount or "import" a volume, and in the case of disaster recovery force a volume from a crashed NAS to mount on another NAS.

I agree on both points (unclear documentation on export and missing functionality), and have raised this issue before (back in 6.4.0 days).

 

Another case that has created problems in the past - sometimes users have exported volumes by mistake, and were unable to get them remounted in their NAS.  A reboot is supposed to resolve that, but apparently it doesn't always work.

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Re: Moving an EDA500 Expansion Chassis to a New NAS

The only thing missing from the process I went through is how to add the share to the GUI so that permissions can be set.  If somebody can share the secret to that, the process I went through above should work.

 

 

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Re: Moving an EDA500 Expansion Chassis to a New NAS


@Sandshark wrote:

The only thing missing from the process I went through is how to add the share to the GUI so that permissions can be set.  If somebody can share the secret to that, the process I went through above should work.


Did you try creating a share with a different name?  Then delete the subvolume from ssh, and rename the original subvolume to match the share name.

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Re: Moving an EDA500 Expansion Chassis to a New NAS


@StephenB wrote:

@Sandshark wrote:

The only thing missing from the process I went through is how to add the share to the GUI so that permissions can be set.  If somebody can share the secret to that, the process I went through above should work.


Did you try creating a share with a different name?  Then delete the subvolume from ssh, and rename the original subvolume to match the share name.


I misspoke a bit.  There is a need to get the whole volume recognized by the GUI, not just a share.  I find it odd that I can create a new volume "behind the scenes" with SSH and mount it such that the GUI recognizes it, but I cannot mount an assembled one.  Everything works as desired from SSH, so data can be recovered to another volume, but the volume cannot be made visible to the GUI so you can just move on using it like any other volume. 

This works:

     mdadm --create the RAID array

    mkfs.btrfs the volume 

    mkdir the mount point

    mount to the mountpoint

     then add the mount to /etc/fstab

The volume is visible to the GUI, including surviving a reboot.

But if you substitute mdadm --assemble --scan for creation and skip making the file system (since it's already there), the GUI doesn't see the volume, even though it's completely accessible via SSH.  I don't think it survived a reboot (RAID had to be reassembled again), but I'm foggy on that since it didn't really matter without GUI recognition.

 

I have found some information saying that an mdadm RAID can be re-created using the same parameters as when it was orignally created, normally reserved for when re-assembly doesn't work.  I've not tried that, as it is clearly documented as a last-ditch effort to recover an otherwise unrecoverable array.

 

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Re: Moving an EDA500 Expansion Chassis to a New NAS

So many thanks to both StephanB and Sandshark!

 

The short answer to the problem of trying to recover a volume on an EDA500 when the host NAS has crashed (so the volume on the EDA cannot be EXPORTED) is that it is very difficult. And therefore it is not wise to use, as I did, an expansion chassis to backup the volume on the host NAS . . .   A second NAS (using rsync) or USB or eSATA drives are reliable solutions (with rsync being 2 1/2 times faster than to drives attached to the NAS).

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