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Re: Do ReadyNAS backup jobs work like Time Machine?

RNUser76
Aspirant

Do ReadyNAS backup jobs work like Time Machine?

Do ReadyNAS backup jobs work like Time Machine?

 

Specifically, do ReadyNAS backup jobs first create a local snapshot, which is then used to backup to an external drive?

 

Like this:

"Time Machine makes hourly snapshots of files and copies them to a backup drive."

http://www.creativetechsupport.com/help/it/install/timemachine-inherit.html

 

My concern is if I add files to a ReadyNAS device at the same time it is running a back up job to an external drive. Is this a good/bad idea? How does ReadyNAS handle this? Any tips on configurations to make this possible/better? etc?

 

For example, is running an overnight task to backup files from a Mac/PC to a ReadyNAS run *at the same time* as the ReadyNAS is running a backup job to an external drive?

 

Thanks

Model: ReadyNAS-OS6|
Message 1 of 12
Sandshark
Sensei

Re: Do ReadyNAS backup jobs work like Time Machine?

On a "push" backup (internal to external), which is what I believe you are describing, yes.  I'm not sure if it does on internal to internal.

 

That is an advantage of using a push backup.  But the downside is that you have to make sure the backup device stays on for the duration of the backup, so powering it via a schedule is challenging.

Message 2 of 12
StephenB
Guru

Re: Do ReadyNAS backup jobs work like Time Machine?


@Sandshark wrote:

 I'm not sure if it does on internal to internal.

It would if you set up rsync, and make the destination the "remote" system. 

 


@Sandshark wrote:

But the downside is that you have to make sure the backup device stays on for the duration of the backup, so powering it via a schedule is challenging.


Correct, so I just use the "pull" backup jobs and live with the risk.  My backups are made daily (midnight), and it's very rare for something to be changing on the main NAS at that time.

Message 3 of 12
RNUser76
Aspirant

Re: Do ReadyNAS backup jobs work like Time Machine?

Thank you for the clarification!


@Sandshark wrote:

On a "push" backup (internal to external), which is what I believe you are describing, yes.


Yes, I was describing a "push" backup (internal ReadyNAS to external drive)

 


@Sandshark wrote:

But the downside is that you have to make sure the backup device stays on for the duration of the backup, so powering it via a schedule is challenging.


What do you mean by "powering it via a schedule is challenging"?

 

Any tips to make a "push" backup (internal ReadyNAS to external drive) run smoothly, if I'm backing up computers to RN overnight while backing up the RN to an external drive?

 

Message 4 of 12
RNUser76
Aspirant

Re: Do ReadyNAS backup jobs work like Time Machine?

Thank you for the clarification!

 


@StephenB wrote:


My backups are made daily (midnight), and it's very rare for something to be changing on the main NAS at that time.


May I ask what happens when that "very rare" event occurs? Errors? Conflicts? Any tips to smooth the bumps?

 

When do you backup to your RN? What if something (big) is backing up to your RN (or changing on your RN) when midnight hits?

Message 5 of 12
StephenB
Guru

Re: Do ReadyNAS backup jobs work like Time Machine?


@RNUser76 wrote:

What do you mean by "powering it via a schedule is challenging"?

 


@Sandshark and I are both backing up to other ReadyNAS.  My backup NAS are on a power schedule, so they only turn on when its time to do the backups, and shut down after they complete.  

 

What is challenging about "push" backups is that the backup NAS has no idea when the backups will finished.  So they don't know when to shut down.

 

That won't affect you if you are backing up to external drives.

 


@RNUser76 wrote:

 

Any tips to make a "push" backup (internal ReadyNAS to external drive) run smoothly, if I'm backing up computers to RN overnight while backing up the RN to an external drive?

 


If you are in the middle of backing up a computer when the ReadyNAS backup starts, you won't get coherent results on the external drive. 

 

So you'd want to start the external drive backup first.  Then you won't get the most recent computer backup, but the external drive will have coherence (not catching any backups in the middle).

 

There is a bug with push backups at the moment, so you'd want to avoid 6.10.4 and 6.10.5 firmware (using nothing newer than 6.10.3).

Message 6 of 12
RNUser76
Aspirant

Re: Do ReadyNAS backup jobs work like Time Machine?

Oh, interesting...

 

To clarify, I'm currently using the RN's SMB backup to another NAS. I may use the RN's USB backup option directly to an external HD.

 


@StephenB wrote:

So you'd want to start the external drive backup first.  Then you won't get the most recent computer backup, but the external drive will have coherence (not catching any backups in the middle).


If I start the backup from the RN to the external drive first, as you suggest, does that job need to finish before I start the backup job from the computer to the RN? Or can these jobs overlap?

 


@StephenB wrote:

There is a bug with push backups at the moment, so you'd want to avoid 6.10.4 and 6.10.5 firmware (using nothing newer than 6.10.3).


Good to know, thanks.

 

Are you referring to this bug? https://community.netgear.com/t5/Using-your-ReadyNAS-in-Business/Backups-not-working-yet-status-says...

 

If so, that appears to be an rsync only bug, correct? It shouldn't impact other types of push backups from the RN (e.g. via SMB or USB)?

Message 7 of 12
StephenB
Guru

Re: Do ReadyNAS backup jobs work like Time Machine?


@RNUser76 wrote:

If I start the backup from the RN to the external drive first, as you suggest, does that job need to finish before I start the backup job from the computer to the RN? Or can these jobs overlap?


The jobs can overlap.  Remember that the "push" job begins by making a snapshot, and then backs up the snapshot (then deletes it when finished).

 

As long as the RN backup begins before the computer backup, the snapshot would be coherent.

 


@RNUser76 wrote:

 

 

Are you referring to this bug? https://community.netgear.com/t5/Using-your-ReadyNAS-in-Business/Backups-not-working-yet-status-says...

 

If so, that appears to be an rsync only bug, correct? It shouldn't impact other types of push backups from the RN (e.g. via SMB or USB)?


That's the one.  I'm not sure if it only affects rsync or not (I haven't tested it myself).

Message 8 of 12
aaroam
Aspirant

Re: Do ReadyNAS backup jobs work like Time Machine?


@StephenB wrote:

@RNUser76 wrote:

If I start the backup from the RN to the external drive first, as you suggest, does that job need to finish before I start the backup job from the computer to the RN? Or can these jobs overlap?


The jobs can overlap.  Remember that the "push" job begins by making a snapshot, and then backs up the snapshot (then deletes it when finished).

 

As long as the RN backup begins before the computer backup, the snapshot would be coherent.

 



ReadyNAS "push" backup seems to be inconsistent with what happens with Mac Time Machine: Remember that the "push" job begins by making a snapshot, and then backs up the snapshot (then deletes it when finished).

 

Try this: With a fresh ReadyNAS, load it up with data and immediately setup and run a "push" backup job to another NAS via SMB (although other connections may work like this, too). There's no delay, the job starts immediately transferring data to the backup NAS.

 

With Mac Time Machine, there's an extended lag time in the "Preparing" stage, especially on the first backup, before data begins transferring.

 

"If a Time Machine backup takes longer than you expect
Your first backup might take a long time, depending on the number of files to back up."

https://support.apple.com/en-us/HT204412

 

"Time Machine - Preparing takes forever… (> 6hours)"

https://apple.stackexchange.com/questions/391948/time-machine-preparing-takes-forever-6hours

Model: ReadyNAS-OS6|
Message 9 of 12
StephenB
Guru

Re: Do ReadyNAS backup jobs work like Time Machine?


@aaroam wrote:
ReadyNAS "push" backup seems to be inconsistent with what happens with Mac Time Machine:

I don't understand your point.

 

Time Machine appears to be building a list of what to back up before it begins.  That isn't unusual - Acronis TrueImage (which I use) appears to do the same. But the ReadyNAS works differently - instead it looks at each file's metadata as it goes, and makes a decision on the fly on whether it should back up that file or not.

 

Two different approaches, but nothing wrong with either one.

 

Message 10 of 12
aaroam
Aspirant

Re: Do ReadyNAS backup jobs work like Time Machine?


@StephenB wrote:
But the ReadyNAS works differently - instead it looks at each file's metadata as it goes, and makes a decision on the fly on whether it should back up that file or not.

 

Two different approaches, but nothing wrong with either one.

 


How can you write to the ReadyNAS while the ReadyNAS is making decisions at the same time about what to backup? Looks like a huge potential for conflicts to write to a ReadyNAS while it is backing up.

Message 11 of 12
StephenB
Guru

Re: Do ReadyNAS backup jobs work like Time Machine?


@aaroam wrote:


How can you write to the ReadyNAS while the ReadyNAS is making decisions at the same time about what to backup? Looks like a huge potential for conflicts to write to a ReadyNAS while it is backing up.


The heavy lifting is all done by the BTRFS file system used by the NAS.  The backup application itself doesn't need to worry about maintaining coherency while the backup is running - the file system takes care of that.  All the backup job has to do is create the snapshot, and back it up.

 

A somewhat simplistic explanation:  When the snapshot is first created, the snapshot and share jointly "own" all the data blocks. That is, the metadata in the snapshot and in the main share both point to the same underlying data blocks. The creation is quite fast, and uses essentially no disk space.

 

As data in the main share changes, the changed data is written to new data blocks (using the "copy-on-write" feature of BTRFS). The original blocks are preserved, and are still referenced by the snapshot metadata. The new data blocks are only referenced by the main share. Unchanged data blocks continue to be referenced by both the main share and the snapshot.

 

The net result is that the snapshot always has the content that was in the main share when the snapshot was created.  Changes only show up in the main share. Disk usage is the total of the original share contents plus any changes made in the main share after the snapshot was made.

 

When the snapshot is deleted after the backup completes, data blocks that are only referenced by the snapshot are reclaimed as free space.

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