Tape allocation in NBU

[V4]

Recently i came to very strange issue at one of my NBU customer.

They are using LTO3/4 as their destination media to write the data and is having NBU 7.1/6.5 in their premises.

they are in process of routing their backup data off production network to SAN.

Presently approx 5+TB of data is taking 4 days to complete. Issue is if backup is initiated by 7.00 AM in monday morning and keeps on running till wednesday or thursday with using LTO001 -LTO003 Tape.

On monday from morning 7.00am till midnight 00.00AM backup writes on LTO001 and asks for another media even though media is not full..

Initially i thought due to previous images  would be on same media and would not allow NBU due to it's nature (LINEAR). But we tried using medias from scratch. because of this whr backup should complete within 2-3 tapes it keep on seeking more media...

any idea how can i get this addressed.

[Marianne]

Check all policies to see if more than one pool is specified. Different pool will use different media.

Check to see if more that one Storage Unit is used - media servers do not share media by default (this can be enabled). Different tape drives are probably configured with different densities and will also require different storage units. Each of them will use media that matches the STU and drive density.

Check schedules for different retention levels. NBU does not mix retention levels on media, unless explicitly enabled.

[V4]

Hi marianne

I took above in consideration, but as we have limited media resources allocation hence we have already enabled allow multiple retentions and media sharing amongts media server.

One pool is allocated to multiple policies so i need to get rid of this exess use of media. Marianne can u pls suggest best way to optimize my allocation. So i can reduce the media usage.

[demo4119]

the usage of the number of tapes depend on your policies retention and max concurrent drives u set for the storage unit and number of media server u have.

When backup from different media server will use different media tape id.

anyway how many media server and lto drive do u have in your environment?

[V4]

there are 4drives (in 2*2 set.) and both are connected to one each media/master server

 i.e.  7.1 Master/Media & 6.5 Media server respectively

[Marianne]

If you have 2 Media servers and 4 tape drives, you really want to ensure that ALL drives are used to get backups done as quick as possible - that is why the customer invested in a SAN, right?

I don't understand what the 2*2 means? 2 media servers allowed to use 2 drives each?
Or 2 LTO3's and 2 LTO4's?

If you REALLY want to limit media usage, you can open the Volume Pool properties and specify Maximum Partially Full setting. If you set it to 1, only one tape will be allocated at any point in time. One media server will write on one drive to one tape, fill it up, mount the next tape.  All other jobs will queue till media server 1 is finished, then media server 2 can start to append to the last tape that was used.

This way you will accomplish what you asked for - write to one tape, fill it up, then only start using the next tape. But then you might as well have one master/media server with one tape drive.

If you want to ensure that all 4 tape drives are used to get backups done ASAP, a MINIMUM of 4 tapes will be used. If the tape drives are LTO3 and LTO4, there will be different Storage Units, different density tape drives with matching density media. Depending on what the config looks like, this will increase media usage.

My opinion:
Your customer has invested in a SAN to get backups done ASAP. It does not quite make sense to me to limit drive and media usage just to save on media...
Also - Allowing multiple retentions per media will save a bit of media initially, but will cost dearly in the long run. Imagine the following : 90% of a tape filled with daily backups with retention period of 2 weeks and 10% occupied by a yearly backup with retention period of 5 years. When the daily backups expire, the tape cannot be overwritten/re-used until ALL images on the tape have expired at the end of 5 years....