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LTO6 tape/volume compression size

Raju_la
Level 5

Hello,

 

As per vendor new lto6 storage capacity of 2.5 TB (native) and up to 6.25 TB (compressed). i belive the compression is enabled by default. so we run the backups to that pool and noticed few tapes exceeded 2.5TB ( Attached the screen shot )  which is good but when i run another client backup to same pool/media it failed

stating unable to allocate new media.

Question - We know that no other scratch tapes are available for LTO6 but why can't the new backup job utilize the existing LTO6 media because there is plenty of room in there?  any sort of setting required in policy to check the writable/used tapes before checking the scratch tapes ??

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Nicolai
Moderator
Moderator
Partner    VIP   

I have heard of  bug that caused large tape to display incorrect values in the GUI from a fellow Netbackup user, but I do not have T/N to support this.

Basically the variables in the GUI can't hold a value big enough and overflow. May CRZ og MPH999 can confirm this.

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14 REPLIES 14

Raju_la
Level 5

Another point just noticed to add. All of the attached tapes are marked as FULL , to me its strange becauase these are brand new tapes ( not like old images are there and reached end of media ) and none of tape reached near 6TB.
 

SymTerry
Level 6
Employee Accredited

NetBackup is not aware of the space on a tape. It is told by the hardware that its full and then a new tape is requested by NetBackup.

The reason NetBackup can't know is it's not handling the hardware compression. Depending on the type of data your backing up, compression will be different and therefore different amounts of compressed data will be stored on tapes. 

Dan_42
Level 4
Partner Accredited

For LTOX (where X can be anything), as you noted, you get two numbers: native and compressed. The unfortunate reality is that some data is compressible, some isn't. For example, I have some clients that back up lots of pictures. This data doesn't compress well (most major formats are already compressed by nature), and they get very close to native storage on the tape. As a general rule, I tell people that if you're getting at least native amount (2.5TB in this case) of data on a tape, that's all the more you can count on. Anything beyond that should be considered fortunate and based on the data you're backing up. 

Do you have reason to believe the data you're backing up is particularly compressible? 

SymTerry
Level 6
Employee Accredited

NetBackup doesn't make a "tape is full" determination. See this connect thread about How much free space in a tape

Raju_la
Level 5

the majority of the data we backing up to these are  jpg word excel stuff. true that compression is handled by hardware but NB, its strange that LTO6 used only 34gb ( second tape in the picture ) and reporing its full

wondering isn't it something wrong ??

Dan_42
Level 4
Partner Accredited
As earlier mentioned, netbackup has ideas about what should be on the tape, but ultimately it defers to the tape drive for tape status and such. Was this tape ever used before, perhaps in another backup system? Or is it fresh out of a box?

Nicolai
Moderator
Moderator
Partner    VIP   

It could also be that the new backup request was with a retention not previous used. Since Netbackup sort backup per retention and no new free tape exist the backup will fail with status 96.

Raju_la
Level 5

"Was this tape ever used before, perhaps in another backup system? Or is it fresh out of a box?"

No, this is delievered month back from vendor so its fresh out of box.

 

"It could also be that the new backup request was with a retention not previous used."

the new backup which is failing has same retention has of all of images on that LTO6. basically we dedicated

these LTO6 pool for few critical file servers. Here even 34gb written LTO6 reporting as full so it doesn't matter about retention too.

 

who is the best company to work with about this possibel issue/ find out the reason behind this thing ( Symantec or Tape drive  vendor ( IBM ) or tape/media vendor.

 

thanks,

Raj

 

 

Mark_Solutions
Level 6
Partner Accredited Certified

It is the tape drive that reports that the tape is full - NetBackup has no control over it at all - get your tape library vendor involved

It may just be a tape drive firmware issue

Raju_la
Level 5

let me find out the possible cause of this with IBM.

Raju_la
Level 5

just noticed another strange part of this issue. when i run the cmd about this tape its showing total written is

4.3TB so GUI & CLI reporting is mismatch ( attached the screenshot ) so this is NB reporting issue .

GUI - written is

CLI - written is   4.3TB

 

Nicolai
Moderator
Moderator
Partner    VIP   

I have heard of  bug that caused large tape to display incorrect values in the GUI from a fellow Netbackup user, but I do not have T/N to support this.

Basically the variables in the GUI can't hold a value big enough and overflow. May CRZ og MPH999 can confirm this.

CRZ
Level 6
Employee Accredited Certified

Yes!  It sounds like this one:

Known Issue: NetBackup Windows GUI reports incorrect kilobyte size for LTO6 media when data exceeds 4 terabytes in size.
 http://symantec.com/docs/TECH213953

You can apply 7.5.0.7 to resolve it.  (I am assuming you're at some earlier 7.5.0.x - please always include an explicit version when you start a thread here on Connect!)

Please give Nicolai the solution; I never would have found this without him prompting me!

By the way... why obscure the media IDs and not the barcodes?  ;)

Raju_la
Level 5

thank you Nicolai and all for ur help.