Verifying Disk Retention for Netbackup

[mulliganx]

Currently we are running Netbackup 7.5 0.6 - We have all of our backups going to disk on a storage unit.  Monday - Friday everyday we are running Duplication which is moving the images from disk to tape. 

Our individual policies have a retention period which varies between 1 week, 1 month, 1 year. 

Everything is being moved daily from disk to tape, however I cannot see that we have any retention on the disk itself. 

What do I need to do in order to allow a 3 month retention on disk, and how can I verify what my current retention levels are?

I have been googling this and have not found the right answer.  Also we are not using SLPs. 

T

[RamNagalla]

how duplication is happenig from disk to tape?

it looks like you are using Disk staging enable on the storage unit...

if yes.. Netbackup use disk as temparory staging area and does not hold any retenctions.. and it manages the space based on the high and low water mark vaulues..

when ever disk space utilization reaches the high water mark, it automatically removed to the duplicated images from the disk and make space for next backups.. and the retenction applies to the tape images..

if you want to keep the retection on the disk, disable  the disk staging and use Vault/manual duplication /scripting to duplicate the images..

NOTE:- make sure you have the enough space in the disk to hold the images to the required retenction.. if that is not the case.. you will run out of space issue and end up with backup failures.. 

[mulliganx]

You are correct.  We have the low water mark at 80% and the high water mark at 90%. 

Duplication continues to remove images off of the disk and onto tape between monday - friday. 

We currently are about 15% space used on the disk, and about 85% free.  

To me it seems like duplication is outpacing the images that are being backed up to disk.  

This is really where my confusion is.  

Is it a bad thing that duplication is moving the images from disk to tape and outpacing the need for the use of a high/low water mark?  

Also, is it best practice to have retention of images on disk?  

If need be, we could always restore from tape..

[RamNagalla · Accepted solution]

hi,

below are my finding on the low water mark, and this will expline why the current usage of disk is 15% even the low water mark is at 80%

7.5 netbackup unix admin guide 1, page 500

Low water mark storage unit setting

The Low water mark setting has no effect unless backups are written through a

storage lifecycle policy, using the capacity managed retention type. NetBackup

copies expired images to a final destination storage unit to create space.

Once the High Water Mark is reached, space is created on the disk storage unit

until the Low Water Mark is met. The default setting is 80%.

See “Capacity managed retention type for SLP operations” on page 574.

The Lowwatermark setting cannot be greater than the Highwatermark setting.

For the disk storage units that reference disk pools, the Low water mark applies

to the disk pool.

page number 517

The high water mark works differently for the BasicDisk disk type. NetBackup

assigns new jobs to a BasicDisk disk staging storage unit, even if it is over the

indicated high water mark. For BasicDisk, the high water mark is used to

trigger the deletion of images that have been relocated. NetBackup continues

to delete images until the disk reaches the low water mark.

Note: The Low water mark setting does not apply to disk staging storage

units.

you need to trun off the disk staging schedule and make use of Vault or Manual duplication (via scripts) to have the images on disk for specified retenction.

[mulliganx]

So you are saying based on the administration guide that duplication can move images from disk to tape WELL beyond the low water mark value? Also is it best practice to have disk based retention even though the data is being retained on tape?

[RamNagalla]

correct..

and if your disk have the enough space to have the disk based retenction.. yes...too...

Disk based retenction should not get the space issue..for the backups.. so if you have the enough disk space.. go ahead..

[Marianne]

Please understand that duplication does not move backups from disk to tape.

Duplication (via disk staging) is exactly that - a duplicate copy that leaves the backup on disk until:
1) High water mark is reached and backup was successfully duplicated
2) normal retention level specified in the policy schedule is reached (whether duplication was successful or not)

See these 2 TNs for more info on DSSU:

Disk Staging Relocation Behavior: http://www.symantec.com/docs/TECH44719

Disk Staging Cleanup Behavior: http://www.symantec.com/docs/TECH66149 

What do I need to do in order to allow a 3 month retention on disk.....

You need to have Advanced Disk license so that you can create SLPs. Only SLPs allow you to have different retentions for disk and tape.