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What is OST media?

Created: 17 Apr 2013 | 6 comments

Do anyone know what is OS media?

 

In my environemnt, BE server create backup job to backup VM to deduplicaton storage.

Open Backup Exec button -> Configuration and Setting -> Audit Log

I found several message about "OSTXXXXXXX has been overwritted" happened when backup job was started to run. Please refer to attachement

What is "OSTxxxxx" ?

 

A lot of message about "disk lifecycle management (backup set retention)" were found in audit log as well. 

Do these messages means deduplication reclamation (free up disk space) happen at this time?

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teiva-boy's picture

OST, Open Storage Technology, is the moniker used when referring to deduplication from Symantec.  The media ID's to identify themselves start as you pointed out as OSTxxxxx.

Data as it meets it's DLM (Data Lifecylce Management) can be recycled and in your case overwritten as it expires.  

There is an online portal, save yourself the long hold times. Create ticket online, then call in with ticket # in hand :-) http://mysupport.symantec.com "We backup data to restore, we don't backup data just to back it up."

steven_man's picture

OST media must be overwritten when backup jobs start?

what is the schedule of DLM (Data Lifecycle Management) for expire image? The expire image is deleted immediately when the backup set expire ? or wait for specfic schedule?

Refer to attachment in previous post, the schedule of DLM is different from the schedule of deduplication storage (12:20 AM and 12:20 PM).

During this DLM, the disk space from deduplication will free up disk space immediately?

For example, one backup job was started at backup at 9:00PM  on 1 Jan and completed at 10:00 PM on 1 Jan . The retention period is 1 day. The backup set should be expired at 2 Jan 10 PM. Do it means that DLM would be ran on 2 Jan 10 PM? Then I can the entry in audit log from Backup Exec 2012 in the same time.

 

teiva-boy's picture

On the backend of things in regards to dedupe.  You have these "container files."  (*.bin)

They are a certain size (I don't recall off hand, but it emulates AIT tape media).  They fill up with deduplication data, and as it fills up, a new .BIN is created.  The full size is allocated up front to prevent file fragmentation.

So now you have hundreds or thousands of *.BIN files of about 100MB or so each.  Data expires in your DLM, but only the markers in the database/catalogs get marked as expired/overwrittable data within the container.  The container is still 100MB.  Again to prevent file fragmentation.

You could have a number of half full or even "empty," container files, but they still consume a fixed amount of space, 100MB.  You have to wait for the weekly garbage collection to compact and free up space, or you can run it manually.  This will go into the containers and try to consolidate the *.BIN's to make them all full.

So now you know the backend, on the front end you have your OST media files, that map to a piece of physical media (.bin).  Data will be updating, overwriting, or appending to existing containers based on the retention of the media sets, as well as the segments/bits of data that make up the container file.

 

(Sorry many of your question related specifically to DLM, and I don't know it well enough, but PKH has written a decent article on them, in the blogs or article section of the forums)

There is an online portal, save yourself the long hold times. Create ticket online, then call in with ticket # in hand :-) http://mysupport.symantec.com "We backup data to restore, we don't backup data just to back it up."

steven_man's picture

teiva-boy,

 

The schedule of garbage collection is weekly? not daily? 12:20 AM or 12:20 PM?

Can you find the task of gatbage collection (dedupliction) from log?

teiva-boy's picture

In 2010 it was weekly, but the dedupe implementation was so poor, folks had to run it manually twice a week or more.

Not sure what it is in 2012, but I assume still weekly.  You can run it manually via the commandline.  The support knowledgebase has info on the commands and process

There is an online portal, save yourself the long hold times. Create ticket online, then call in with ticket # in hand :-) http://mysupport.symantec.com "We backup data to restore, we don't backup data just to back it up."

Larry Fine's picture

Open Backup Exec button -> Configuration and Setting -> Audit Log

I found several message about "OSTXXXXXXX has been overwritted" happened when backup job was started to run. Please refer to attachement

OST media are kind of "special".  They are kind of like B2D images and kind of like tapes.  Basically, OST media/images/files are single use.  Internally, they cannot be appended to or overwritten.  In place of that, when BE wants to re-use an OST media, it retires it, deletes it and recreates a replacement with the name name/number.  To the user, it simply appears that the media was overwritten. The retiring & deleting get logged in the audit log, sample below.

 

4/4/2013 1:43:09 AM        server8\Administrator      Device and Media      Media : OST00000392-419321DDBA43EE36 has been moved from media set Internal Disk Images to media set Retired Media.

4/4/2013 1:43:09 AM        server8\Administrator      Device and Media      Media : OST00000392-419321DDBA43EE36 has been deleted.

4/4/2013 4:30:26 AM                                      Device and Media      Media : OST00000392-419321DDBA43EE36 has been overwritten by job OST1 Backup 00006-Full.                        
 

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