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Free space on tape


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Likely a noob question, but just want to be sure things aren’t broken.

I’ve got a setup with Veeam B&R Community Edition on a single windows machine. I have full backups scheduled weekly, and daily backups every day, to a Quantum LTO-7 drive, using LTO-6 media.

The console reports the total capacity of the tapes as 2.1TB. Allowing for the whole base 10 / base 2 argument, this is what I’d expect. 

The full backup (done last night) reports total transferred is around 1.1TB, but the tape is only reporting around 250GB free. I’m expecting around a TB free (2.1TB - 1.1TB). 

You can also see that the “daily” tapes are reporting 2.1TB free (again, this is expected - there’s not a lot written, maybe ~90MB per day, so not enough to make a difference to the free space reported)

Is there something amiss somewhere, or am I going to have to migrate to LTO-7 media a lot sooner than I thought?

 

 

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Best answer by Dima P. 28 November 2022, 21:32

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Userlevel 7
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Posting in the R and D forms might really help you. There are some smart Veeam employees that frequent the tape section and if you provide your case number they might give you some insight. 

Hey @Scott  → I’ve sent this thread to the tape PM; no need for duplicate posting.

Userlevel 7
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Posting in the R and D forms might really help you. There are some smart Veeam employees that frequent the tape section and if you provide your case number they might give you some insight. 

Hey @Scott  → I’ve sent this thread to the tape PM; no need for duplicate posting.

My bad Rick. Didn’t see that. 

Hi guys!

The free space is reported by the drive based on End of Media attribute, so there is no mystery why B&R uses the set amount of storage. Simply because it was told by the tape > drive > library :)

  1. You may have additional partition created by any other software which ‘blocks’ full tape capacity. To deal with that you need to full erase the tape via vendor tools (i.e. reformat the tape)
  2. While the tape lifespan is decreasing the bad blocks are being recognized/noted by the drive and excluded from capacity. Could be the issue with either tape being old or drive being dirty. 
  3. Human error (I bet that’s not the case, but still): marketing capacity always doubles the actually tape free space due to the possible compression savings. B&R displays native capacity available on tape. Say for backup files compression takes no effect anyway as we compress data during backup to disk

Based on the description I’d go with cleaning / tape lifespan investigation.

Userlevel 7
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All hail reply from @Dima P. 

Userlevel 2

Hi Dima,

Definitely not any of the problems you’ve mentioned.

The tapes are genuine Quantum ones fresh out the box. I have 8 tapes total in the pool, which are rotated so that they all see 1 weekly backup and 6 daily backups in an 8 week cycle. The backups have been running for about 14 months, so each one has only seen 7 or 8 cycles. It’s exactly the same on a brand new un-opened tape too. 

Cleaning is done at the end of an 8 week cycle, well before the drive requests it. 

The free space is reported correctly when the tapes are empty, so nothing to do with extra partitions etc.

And not human error either, The tapes are LTO-6, so NATIVE capacity is 2.1TB.

If you’d read my original post, you’d have realised most of this.

So despite the “Solved” icon at the top of the screen, this issue most definitely is NOT solved.

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