Unsolved
This post is more than 5 years old
4 Posts
0
3240
Iseries backing up to DD using BRMS
We backup to a DD670, OS level 5.4.2.1-423209
My question is, when does the data get removed from the data domain disk and frees up the storage?
I thought that when you expire a tape in BRMS, it would free up the data on the data domain, but that is not the case.
If you backup up to a tape, expire that tape but never use that tape again, does it always retain its storage on the Data Domain?
I ended up initializing the expired tapes in BRMS. which freed up the space on the Data Domain. So, I guess this is the only way?
jbrooksuk
208 Posts
0
August 27th, 2014 01:00
Hi,
If the tape is set as 'expired' by the backup application, then this is just essentially a flag that only the backup application knows about.
Until new data is written from the beginning of the tape or the tape is relabelled (initialize as you have done in your case) then your DDR will not know that the data is no longer required and therefore the data will remain on the tape and will be held by the DDR.
Essentially, rewind to BOT followed by 'a' write from there is the only thing that will tell the data to be removed from the tape and thus disk space, as far as the DDR is concerned.
WIth any VTL system, you should always aim to keep only the amount of tapes that you need and overwrite them where possible to avoid any manual steps to free up that space. This behaviour is not unique to DDR VTL, it is in essence the same for physical tapes and also EDL/VTL, which EMC sold before DDR's.
Regards,
Jonathan
PeterWirth
14 Posts
0
August 27th, 2014 02:00
As Jonathan described correct, expired means only that the retention time for a particular backup set has reached and the tape can now be reused for another backup. You can use the tape for further restores, as the data is still there (and so on Data Domain).
Furthermore BRMS will always try to use new tapes before overwriting expired tapes. This comes from the physical world, as new tapes are normally better than "old", used tapes.
For a VTL environment this means to create not too many tapes in advance, so the expired tapes are reused again and space is reclaimed on DD.
There is a new option available for BRMS called "Initialize on Expiration" or INZONEXP, which will exactly do what it is called. Maybe this is a good fit for you, you can Google for a detailed description.
Hope that helps!
Peter
bhumm1
4 Posts
0
August 27th, 2014 07:00
Thank you Peter, most helpful.
bhumm1
4 Posts
0
August 27th, 2014 07:00
I understand, all makes sense. Thank you.
bhumm1
4 Posts
0
September 2nd, 2014 07:00
Peter,
I have been initializing all my older tapes on my iseries partitions to free up space on the data domain.
After this process, I look on the data management summary screen on the DD and see I have 5 TB of usable space and 10 TB of cleanable space. When I run the cleanup, which takes 24 hours, the 10 TB of cleanable space is down to .25, but the usable space hasn't increased at all. When I look at the space usage graph, I see a good decrease in pre comp used space, but I don't see a change in the summary screen. Am I doing something wrong?
Thank you.
Bruce
ble1
14.3K Posts
0
September 2nd, 2014 08:00
Cleanup happens at several stages. When using backup application with DD you have two stages:
- application
- DD
DD cleanup cannot happen before the one in application. Unless you do it manually and you are data loss friendly guy
In application, data sets will expire based on policy and dependency in backup cycle (different backup level dependencies to parent full level backup). Once backup cycle is expired, data set which is part of that cycle will be marked expired. Once all parts on various backup cycles on tape are expired, volume can be expired/resued in application.
On DD, volume will not be expired as DD VTL is supposed to emulate PTL and in PTL you can re-scan data back into application even when expired and gone from application catalog. Therefore, volume can be expired at volume level in application, but data must still reside within DD. That's a law. As with any VTL product, key to efficient usability is to have sized volumes at lower size (with DD this is 100G or something a little bit more) and number which is just about right so that volumes are re-initialized fairly quickly after expired. That means your volume will be re-used quickly after marked as reusable which will re-init (relabel) it and this process will also mark data on tape as permanently gone. You can also do this manually and I think you can even schedule it now in recent NW versions for example.
Last, removal of this data from DD is done during cleanup process which typically runs once a week and only data shown as marked to be removed will be usually removed (run df on DD and you will see it how much that is).
Messing around manually on DD outside application is asking for trouble unless you know what you are doing and how dependencies are set.
PeterWirth
14 Posts
0
September 2nd, 2014 10:00
Bruce,
I don't think you did anything wrong. Maybe you're looking at the wrong numbers. If you can send me one of the latest autosupport files to peter.wirth at emc.com, then I will take a look at it.
Peter