What happens with multiple destinations?

[MrPete]

A KB article talks about this for the proactive backup product: http://kb.dantz.com/display/2n/kb/article.asp?aid=5638

 

My question: what happens if multiple backup sets are defined in the Windows Pro product?

 

I'm hoping:

* The backup rotates among the defined sets, based on which ones are actually available.

* So, if you have three external backup drives defined (A,B,C), and two are available (A, C)... it will not complain about B missing, but one day will backup to A and the next to C. Then back to A, etc.

(This example assumes a once-a-day backup schedule)

 

Is this correct? If not, how does it actually work? I don't see this documented anywhere.

 

Thanks muchly

Edited August 30, 2008 by Guest

[Mayoff]

Professional does not have proactive backup, so you use a normal backup script and you schedule each destination to run on specific days. Check http://www.emcinsignia.com/video to learn about schedules

[MrPete]

I appreciate the info. Unfortunately, that didn't answer my question. What happens if multiple backup sets are defined in the destination? I find no documentation of this.

 

So far, what I've learned is that it does not automatically cycle between them.

 

It appears that even if the first is not available, it does not move on to the second one.

 

So, under what circumstances is it appropriate to select two destination backup sets?

 

Thanks.

[rhwalker]

Well, it can cycle if you define an appropriate schedule. That's how you do alternating backups.

[MrPete]

I'll ask a related question.

 

Background: our goal is to make it easy for a non-tech admin to manage cycling between multiple backup devices, swapping them out so some are disconnected (power safety) and/or offsite (disaster safety) at all times.

 

Experience says it is hard to get a non-tech admin to manually synchronize a computer backup schedule and a set of physical devices. So, we want to enable them to simply plug in a device, and know that it will be used for the next backup.

 

QUESTION: Assuming that a "pro" script will only back up to a single defined backup set, is there any downside to the following strategy? (Other than the overhead of "failed" backups?)

 

* If three sets (A, B, C) are to be cycled...

* Create three backup scripts that only differ in their destination.

* Run all three scripts every time

* Two of the three will "fail" due to missing destination; one will succeed.

 

Thanks

[MrPete]

rhwalker, it can cycle using multiple defined destinations? I haven't seen how to do that.

 

Cycling by having different scripts, scheduled at different times... yes, that is easy. To schedule. The hard part is ensuring the right device is plugged in every time. And it puts the backup software in charge of the user, rather than the user in charge of the backup software.

[rhwalker]

The downside is that it doesn't enforce cycling. If set A is left connected all the time, the same result will be observed by the "non-tech admin" (two fails, one success).

 

A better approach is an autoloader with multiple sets loaded, schedule to choose the correct set in the autoloader, get the "non-tech admin" to swap sets in the autoloader.

 

Russ

[rhwalker]

rhwalker, it can cycle using multiple defined destinations?

Yes. Define an appropriate schedule for each destination, one script. (e.g., backup set A, MWF, backup set B, TThSat). Examine the link that Robin suggested.

 

Russ

 

[MrPete]

Now I've learned what actually works and what does not:

 

* Multiple defined destinations determines which destinations COULD be scheduled or selected for a script.

* Any given run (scheduled or manually started) must have one and only one destination selected.

* A preference determines Retrospect's wait for a destination to be placed online. The default is to wait forever (which causes the entire schedule to halt if a backup set is not available). Changing this to a short time (e.g. one minute) means you can schedule nightly backups on all possible devices, if desired.

* A single script can contain parallel schedules for backups to A, B, C on the same schedule. One only has to add a schedule for each destination.

 

Put all of those together and what I want becomes possible. Any combination of:

* Computer forces operator to use a specific backup set on a specific day.

* Operator can place any backup set online on any day.

 

You could even automatically do two backups on the same night if desired, by placing two sets online.

 

My only requests would be for:

* Better documentation of the above; it was not easy to find this info, and it certainly is not documented as part of the possible/available backup strategies. Even though other systems allow it, and "human controlled sequencing" is arguably just as valid as "computer controlled sequencing."

* Simplified configuration of the above, with ability to avoid error messages. Essentially, "back up to one of these sets; only complain if none are available."

 

(rhwalker, yes, a tape autoloader is great for tapes; an "offline" tape would not be destroyed by power glitch/etc. We're beyond tape; external hard drives give higher capacity, performance and cost effectiveness. We also prefer for safety reasons to rotate sets offsite not just offline.)

[rhwalker]

(rhwalker, yes, a tape autoloader is great for tapes; an "offline" tape would not be destroyed by power glitch/etc. We're beyond tape; external hard drives give higher capacity

Nope, not with an autoloader. "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway." Andrew Tannenbaum (1966).

 

performance

Perhaps, for some hardware.

 

and cost effectiveness.

Perhaps in some cases. Not for us.

 

We also prefer for safety reasons to rotate sets offsite not just offline.)

 

So do we. As I suggested,

 

get the "non-tech admin" to swap sets in the autoloader.

That's what we do each day. Saved our butts a few years back when our floor of our office building burned down. No data lost.

 

Russ

Edited September 10, 2008 by Guest

[MrPete]

Wow, what tape technology do you use? Honestly interested.

 

We're spending $175 per TB for high speed/high rel disk. (Seagate external drives)

[rhwalker]

Wow, what tape technology do you use? Honestly interested.

 

We're spending $175 per TB for high speed/high rel disk. (Seagate external drives)

That's about comparable to Exabyte X23 tapes for VXA-320, which are about $60 for 320 GB (nominal) compressed, really about 275 GB in practice. Other technologies (LTO-3, etc.) have bigger autoloaders, etc. I'm seeing LTO-3 tapes (800 GB compressed) at $40 in singles, $762 for pack of 20 (i.e., $38 each for 800 GB). There are big LTO-3 autoloaders around.

 

Russ

[MrPete]

Obviously we've got to cover the drive/loader mechanism, but you're right - incremental on LTO-3 looks good.

 

[MrPete]

Looks like this is a bug.

 

As I noted above, you can configure a schedule for different backup sets, some online, some offline. AND you can configure Retrospect to not wait forever for offline sets.

 

HOWEVER... after all that, it does not work. No matter what I do, Retrospect halts the schedule and waits forever for operator intervention when a backup set is offline.

 

Looks like a bug to report.