Free space on tape

According to the tape drive properties, the block size is 128K - Seems sensible.

Done some analysis on the files, and I have the following results

I have counted 121613 files with a size of 128K or less. If I assume these all take a 128K block, then it amounts to 13.5 GB of wasted space.

For the large files (over 128K), I have counted 23422 files. If I assume each of these might take an extra 128K block in addition to what the actual file size is, to round up to a whole number of blocks on tape, I get another ~3GB of wasted space.

So, worst case, with each “small” file taking one block, and an extra block added on to “large” files, there shouldn’t be any more than 20GB wasted. That’s less than 2% of the 1.1TB total, which is entirely acceptable.

So, I don’t think it’s a block size issue. Even though there are a lot of small files, the numbers just don’t add up. Unless I’ve misinterpreted the 128K, and it’s actually 128M or something.

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.