NBU 7.6 SLP Windows, can it reduce tape usage

[John_Snodgrass]

I'm trying to come up with a way to reduce the number of tapes that are getting used for the duplication function in my SLPs.  I found I had a problem with different tape retention, I fixed that, but I'm still using 4 tapes a night, and none of them are full, in fact two of them only have 6 images each.  I've looked and there are duplications running all over the place at night,.  I was thnking that maybe if I create a window to run them in, it will combine more of them together and hopfully make better use of the tape.

I have three SLP, two for customer backups from two different disk pools, and one for the catalog backups that need to go offsite.  They all have the same retention level for disk and tape.  It used to only take one tape when it was configured to do the duplications from a special vault profile.  The problem there was it would fail or not duplicate some images, so I wanted to use the more failsafe SLP method to control the storage locations, replications to the DR site and the duplication to local tape.  It's working great, just using a lot more of the customers tapes.

Here is some data from the tapes from last night:  (see attched file)

One thing I noticed was that after things crossed over midnight and the date of the data expiration changes it used new tapes.  Would having the duplication all done after midnight make them all the same day?  I would be happy to get it down from 4 tapes to 2.

Any thoughts or comments?

[RamNagalla · Accepted solution]

how many tape Drives you are using for duplication..?

if you have enough bandwith , reduce the numnber of tape drives for SLP duplication to 1 Drive.. so that only one job will be acive and they will be using the same tape untill it gets filled..

other way is use SLP parameters to batch the larger jobs..

Minimum size per duplication job to someware around 1500 GB , and Maximum size per duplication job as 2500 GB or something near to your over night backup size..( do not keep too much )..so that all pending images will become batch and trigger lesser jobs.

[cruisen · Accepted solution]

Hello RamNagalla,

If you reduce the numbers of drives, be aware that the duplication will take longer than, as it will be waiting for the first job to finish before the next starts.

I do not see a problem here. It uses 4 tapes because of 4 drives. And they will get Full over the Time, I hope that the option to not mix retention on tape is set.

NetBackup allows you, but not by default, to mix retentions on a tape - so you can have an incremental with a  2-week retention on a tape mixed with a full with a 1-year retention.

Best regards,

Cruisen

[John_Snodgrass · Accepted solution]

I've changed the MIN and MAX duplication sizes, and I also created an SLP window to run the duplications from midnight to 10am, that should be more then enough time.  I'm hoping this fixes the problem with tapes having different expiration dates from before and after midnight.  If so I think I'll be down to two tapes used per night, I can live with that.

I have 4 LTO4 drives and all backups run to disk, so the tape is only used for duplications to be sent offsite.  We'll have to see how it works tonight.  I changed the max drives to 2 in the STU, but I don't think it was every using more then 1 or 2 at a time anyway.

My only resource contention is the tapes themselves, the customer would prefer to not have to go buy more tapes, but they will if absolutly neccessary.

In doing my research, I saw there was a setting to allow a duplication to run past the end of the window, but I don't recall where that was and I can't find it.  Any help please.  I want to make sure any running jobs will run to completion.

[John_Snodgrass]

Cruisen,

My problem was the tapes are not getting full.  We are sending out 4 tapes with no more then 2 tapes worth od data on them at the most.  If you looked at my attachment you saw that two of them only had 6 images and not that much data.

[RamNagalla]

it will be in SLP window advanced settings

you should be good with MIN and MAX settings ..

[sdo]

IMO, and it is just an opinion, we first need to remind ourselves of two things:

1) From an SLP duplication perspective, the 'workload' of a backup session is a set on 'n' backup streams, that have the principal characteristics of 'size' and 'finish time'.  I.e. backup jobs/streams become eligible for duplication when they finish, and are usually of a varying size.

2) Unless your environment is fairly small, and fairly static, then the size and finish times of backup jobs and streams will vary from one backup session to another, and so... whilst collectively a 'backup session' will typically be the same total job count and same backup clients from one backup session to another, it is the sizes and finish times of the backup jobs/streams within the backup session 'set of jobs' which will vary from one session to another.

So, knowing the above, then IMO, it will be quite difificult to engineer a sweet spot configuration of SLP parameters which results in minimized demand for tape drive usage.  We also need to remember that essentially SLP duplication jobs request/demand a tape drive resource - and so, if 4 tape drives are available then SLP duplication jobs can and will make use of 4 tape drives, if the storage unit concurrent write drive setting of the storage unit is 4.

Also, in my thinking, if one has 'n' tape drives available for write, then in my planning I would always factor in there being 'n' partial tapes at the end of the duplication session.  And unless you are very lucky and have a SLP duplcation job exactly fit a tape media capacity, then there will always be 'n' partial tapes.

I think that the only true way to reduce the number of partially full media is to reduce the concurrent write drives of the tape storage unit.  This will reduce the ability of the SLP engine from using more that the specified number of tape drives, and so reduce the number of partially full media from one duplication session job set to another - no matter what the internal sizes and backup job finish times are within any given backup session and thus duplication session.

[Nicolai]

What about the "Maximum partially full volumes" setting ?

http://www.symantec.com/docs/TECH69376

[sdo]

Another good tip.  :)

[John_Snodgrass]

All of the various changes I made yesterday seemed to work.  There were far fewer duplications that ran, and they were bigger, all as expected.  Setting up the SLP windows forcing the duplications to run after midnight also had positive results.  We did not end up with tapes with different data expiration dates.  End result it only used two tapes last night, which I said I could live with.

Thanks again for eveyones help and suggestions.