Question on Vault, Disk Storage units, and multiple streams

[LToro]

We are running NBU 6.5.3 and we have a rather big backup going to a disk storage unit. It is streamed to break up the backup into 5 chunks. Then we have vault setup to immediately dupe to tape and expire the image. My question is: if one of these streams fails, will the other images remain on the DSU (ie., not be vaulted to tape)? Since we have other backups going to this DSU, we end up getting 129s (DSU full). And that affects all backups going to this DSU.
Thanks

[schmaustech]

Just so I understand correctly:

You have a job that backs up a volume in 5 streams, so in the activity monitor, you would have 6 jobs, the parent/control job and 5 stream jobs.  4 of the stream jobs finish successfully but the 5th one fails with a status 13 (as an example)?

I would think the parent/control job would say this backup was partially successful and the 4 streams that finished would be kept on the DSU until vaulted off. 

Do you get status 129's on that DSU if all streams are successful?

Regards,

Benjamin Schmaus

[Rick_Brown]

Hello,
When the backup starts, depending how the DSSU is setup, the 5 streams all begin sending data.The streams will not start one after the other, but all at once (I'm making some assumptions here) and the disk conpumption begins. The data will load into the DSSU until the highwater mark is hit, then the disk is considered full. You need to consider stagering your DSSU jobs, allowing the destage to tape enough time to keep up with the data being loaded.
Here's what I do:
I have all by small SQL-log backups write to the DSSU once per hour. I destage once per hour to tape - this saves tape drive contention. I can hold approx 2-3 days worth of SQL logs on the DSSU before hitting the highwatermark on most days. Once the high-watermark is reached, NBU removes all the data down to the low-watermark. The cycle begins again.

You need to make sure your not loading more data to the DSSU than you can destage to tape during the same timeframe, making sure you have enough capacity to handle the load. You'll want to monitor the DSSU usage as the day progresses to see how effective your balence is.
It has been my experience DSSU's are perfect for handling several small backups, not large backups. Remember, the large DSSU backup still has to be written out to tape, so why not write out the large backup to tape and be done, rather than tie up the DSSU and then a tape drive for several hours. Watch your watermarks too.

Hope this helps.

[LToro]

Sorry for the delayed response...I was getting alot of spam after registering on this forum...got that rectified. Back to my question:

I am new to this particular NB environment, and an overhaul has been long overdue. In essence, we are getting alot of failures, including 129s. In the end, all backups will be going to DSUs (not DSSUs, as my understanding is that there is a difference). So my concern to the individuals that suggested this roadmap is: if we have 5 streams (each stream is, as an example, 1 TB), and one stream fails (we get 13's on some of these streams), will NB Vault not fault those streams that had RC 0 to tape (in essence retaining 5 TB on disk, even though 4TB were successfully backed up). Now I did notice, upon doing a restore, that the data on the good stream(s) can be restored so my guess is I may have answered my question, since after a vault, the tape copy becomes the primary, and the disk copy is immediately expired.

[LToro]

Rick,

See my prior reply.
Isn't there a difference between DSU ans DSSU? We are using DSUs.

Thanks

[John_Stockard]

Yes, there is a difference between a DSU and a DSSU.

A DSU ("Disk Storage Unit") is a disk location used to hold backups.  The backups live on this disk location until they are expired.  The expiration can occur naturally (i.e., the backup image reached it's retention period) or they can be expired prematurely (i.e., by your Vault job after they get copied to tape).

A DSSU ("Disk Staging Storage Unit") is similar to a DSU in that it is a disk location used to hold backups.  The big difference is that when a DSSU is created, it has a policy associated with it that tells NetBackup where to duplicate the backup images to (the "destination").  This destination can be either tape or another DSU (or even another DSSU).  There is also a schedule associated with this policy that tells NetBackup when to duplicate any un-copied backup images from the DSSU to the destination. 

Another neat feature of a DSSU is that NetBackup will keep the backup images on the DSSU even after they're duplicated to the destination.  The images will be removed from the DSSU once they reach their retention period or if NetBackup determines that it needs to remove duplicated images to make room for new backup jobs (the DSSU's capacity hit the high-water mark).  The rationale for this is to increase the odds that a restore request will be satisfied by a backup image located on disk instead of having to mount a tape,

When the DSSU reaches the high-water mark during a backup operation, the backup is suspended and NetBackup will then start removing the oldest duplicated image from the DSSU until the DSSU's capacity reaches the low water mark.  Once the low-water mark is reached, NetBackup will resume the backups.  If there are no eligible images on the DSSU to delete in order to reach the low-water mark (i.e., the DSSU is full of images that have not been migrated to the destination yet), the backup jobs fail with an error message.

The manual entitled "NetBackup 6.5 System Administrator's Guide for Windows, Volume 1" contains a good description of DSUs and DSSUs in Chapter 5, "Storage units, unit groups, and lifecycle polices".  If your NetBackup master server is running on Linux or Unix, the equivalent manual would be the "NetBackup 6.5 System Administrator's Guide for Linux and Unix, Volume 1".

[rjrumfelt]

We are getting ready to implement a new environment using DSU's and I was wondering if anyone had any advice regarding their setup.  Or, more importantly, any troubles that you have seen with using DSU's as compared to VTL's or physical tape?