Backup my QNAP to a ReadyNAS Duo?

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alokeprasad wrote: I was going to use the Duo (JBOD, RAID 0 with 4 TB capacity) for backing up another bigger NAS.  So I can afford that risk of a drive failure on the Duo. No different that using an external USB drive to backup the Qnap (which I intend to do as well).

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You might be confusing some terms here. JBOD in this context means two volumes (C and D) of 2 TB each.  RAID-0 would be one volume (C) that spans both disks and is 4 TB in size.  The QNAP folks might refer to this differently, but that's the usage here.

We recommend 2 volumes in part because the 4 TB volume is more fragile.  When either disk fails, you'd lose the full volume.  So (all things being equal) the odds of losing everything is about twice the failure odds when using a single disk.  We also recommend two volumes because there are some freeware tools that would let you read the Duo's internal disks from a Windows PC - which is very handy if the Duo itself fails.  Those tools don't support the single 4 TB volume.  

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alokeprasad wrote:

I finally read the manual (page 19)

Maybe next time read it sooner?  The manual includes quite a few step-by-steps, and it is faster/easier to refer to them instead of trying to replicate them here.  This is a community forum; you aren't talking with people who are paid to answer your questions.

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alokeprasad wrote:

I would still like to know how to set up the Duo v1 as a destination for backups (run on the Qnap) using Rsync, or CIFS/SMB or FTP protocols.

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First of all, if you want to run the Duo on a power schedule (instead of leaving it running 24x7), then you will want to run the backup jobs on the Duo instead of the QNAP.  Otherwise you risk having the backup job fail if it starts a bit too early, or runs longer than you expect.   If the backup jobs are still running when the shutdown time arrives ,the Duo will defer the shutdown until they finish.  You would want to schedule the backups to run during a time when you aren't writing files to the QNAP though. 

If you are ok leaving the Duo running all the time, then it doesn't matter which machine does the backup.

Second, on the backups, incremental rsync is best.  One reason is that it preserves the linux file attributes (permissions, owners, etc), much better than the others.  In addition, CIFS/SMB is limited to SMB 1.0 on the duo, which is being deprecated by Microsoft, and at some point might be deprecated on the QNAP too.  FTP isn't a great backup protocol (it was never designed to be one).

To your question - you enable rsync itself in system->services->standard file protocols.  Then you enable rsync on each share on the Duo that you want to use as a backup destination in the QNAP on the system->shares->share listing page.  CIFS/SMB is enabled by default when you create a share.  If you go with my recommendation to use Rsync, then you should turn off CIFS/SMB on the NAS shares. That would give you a bit more protection from ransomware attacks.  With either protocol, you'd need to set the backup destinations of the QNAP to be NAS shares.

Note that if you follow our recommendation to use two volumes in the Duo (C and D), and you will need to create at least one share on each.  You'll want to roughly balance the disk space needed on both volumes, so that they will both have reasonable free space.  If one of the volumes becomes full later on, you'll either need to move some shares around.  My own duo is set up this way, and it's not as burdensome as it might sound. I've shifted shares around only once over the past couple of years.

Since the Duo has less capacity than the QNAP, this will work out better if you have several shares on the Duo, and several backup jobs running (either on the QNAP or the Duo).  Even with one volume, at some point the Duo won't be able to back up everything, and when that happens you can simply delete some of the backup jobs.