cancel
Showing results for 
Search instead for 
Did you mean: 

tape full

PrakashKodali
Level 3

Hi,

Showing LTO5 Tape is full for 2 backups . Each backup is 300GB. Scheduled as weekly backup.Total it is around 600GB. But tape is showing as full, we can not take another backup. we have retention period of 2weeks. older backups should expire and space must be available for the backup.

Kindly help where is the problem.

regards

K.Prakash

 

 

1 ACCEPTED SOLUTION

Accepted Solutions

mph999
Level 6
Employee Accredited

Following on from the excellent answer from the amazing Marianne ...

You explain that the tape shows full after about 600GB.

An LTO-5 tape should hold around 1.5TB uncompressed.  If the data is compressable to say 2:1, it would hold arounf 3TB.

An LTO-4 tape holds about 800 GB uncompressed.  So first question is to make sure this realy is an LO5 tape and not an LTO4 tape.

Presuming it is LTO4, even if the data is not compressable (for example files that are already compressed (.zip) or data that is in a compressed format (.jpeg)) then it is storing less than it should.

If this is the case, simply you have a drive/ driver or firmware problem with the drive.  NBU does not understand tape capacity, it would write to the same tape forever unless it is told to stop by the tape driver.

What should happen, is that when the tape passes the 'logical' end of tape, this is a marker written to the tape during production, that is detected by the tape drive firmware when the tape is 'alomst at the end' eg. Full.

At that point, there is enough tape left to finish writing the block that is being written.  NetBAckup then sends the next block to be written but the tape driver stops this, and reports back to NBU that the tape is full.  It is this, the tape driver telling NBU the tape is full, that makes NBU mark the tape full, and load a new one.  The tape driver knows the tape is full, as it is told so by the tape drive firmware.

You can see from this description, which I can assure you is 100% correct, that there is no way NBU is marking the tape full early.  You need therefore to take this up with the hardware vendor.

This same information is documented offically in the technote :  https://www.veritas.com/support/en_US/article.TECH169477

Search down for the 'Tapes not reaching capacity part'.  Feel free to share this with the hardware vendor, as usually they try and blame netBackup.

Regarding deleting ealier backups, not possible.  As Marianne explained, tapes are written sequentially - something like this, Where Data1 are the blocks for backup1 and Data2 the blocks for backup2.

<Tape Header><Backup Header><Data1><Data1><Data1><Backup Header><Data2><Data2><Data2><Empty Header>

It is not possible to overwrite just the <Data1> blocks with a new backup.  No backup software can do this.  The space on the tape taken up by <Data1> will only be reused when all the backups on the tape expire, and the tape is then free to be overwritten from the beginning.

View solution in original post

2 REPLIES 2

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

When a tape is full, ALL backups on tape must expire before tape can be re-used/overwritten. Space from expired backups cannot be used. 

Please read through this blog: 

mph999
Level 6
Employee Accredited

Following on from the excellent answer from the amazing Marianne ...

You explain that the tape shows full after about 600GB.

An LTO-5 tape should hold around 1.5TB uncompressed.  If the data is compressable to say 2:1, it would hold arounf 3TB.

An LTO-4 tape holds about 800 GB uncompressed.  So first question is to make sure this realy is an LO5 tape and not an LTO4 tape.

Presuming it is LTO4, even if the data is not compressable (for example files that are already compressed (.zip) or data that is in a compressed format (.jpeg)) then it is storing less than it should.

If this is the case, simply you have a drive/ driver or firmware problem with the drive.  NBU does not understand tape capacity, it would write to the same tape forever unless it is told to stop by the tape driver.

What should happen, is that when the tape passes the 'logical' end of tape, this is a marker written to the tape during production, that is detected by the tape drive firmware when the tape is 'alomst at the end' eg. Full.

At that point, there is enough tape left to finish writing the block that is being written.  NetBAckup then sends the next block to be written but the tape driver stops this, and reports back to NBU that the tape is full.  It is this, the tape driver telling NBU the tape is full, that makes NBU mark the tape full, and load a new one.  The tape driver knows the tape is full, as it is told so by the tape drive firmware.

You can see from this description, which I can assure you is 100% correct, that there is no way NBU is marking the tape full early.  You need therefore to take this up with the hardware vendor.

This same information is documented offically in the technote :  https://www.veritas.com/support/en_US/article.TECH169477

Search down for the 'Tapes not reaching capacity part'.  Feel free to share this with the hardware vendor, as usually they try and blame netBackup.

Regarding deleting ealier backups, not possible.  As Marianne explained, tapes are written sequentially - something like this, Where Data1 are the blocks for backup1 and Data2 the blocks for backup2.

<Tape Header><Backup Header><Data1><Data1><Data1><Backup Header><Data2><Data2><Data2><Empty Header>

It is not possible to overwrite just the <Data1> blocks with a new backup.  No backup software can do this.  The space on the tape taken up by <Data1> will only be reused when all the backups on the tape expire, and the tape is then free to be overwritten from the beginning.