Tape Backup Compression

[rklingaman]

I have a question to see if its normal activity or strange for tape Backup.

We backup or .vbk files to tape everyday with NetVault Bakbone. Our veeam jobs do have multiple servers per job to get a decent dedupe ratio online.

The thing that I'm seeing is that on LTO3 tapes I'm actualy getting negative compression so on a 400Gb tape I'm only getting 280GB. I don't expect to ever get anything over 400Gb as they files are already compressed/deduped but was curious if that was normal to drop below the native size.

The last thing I am is married to NetVault so if other people are seeing better with other backup products I would like to know.

Thanks,

Ryan

[TrevorBell]

i get zero compression with backup exec 2010 r2.... lto-5

[rklingaman]

Zero Compression so your getting 1 to 1 the full native 1.6TB on your LTO5?

[tsightler]

We use Netvault Bakbone to write our Veeam backups to tape as well. We typically see between 380-420GB per LTO3 tape so it's surprising you're seeing such low capacity.

[TrevorBell]

sorry for the delay but i get 1:1 backup 1.2tb ( 4 .vbks files ) and it takes up 1.2tb space on a 1.4tb lto-5 tape.

Trev

[FBraendle]

Count me in!
We save our VBKs with netvault to lto4 and i get compression ratios of 0.75:1.
I just opened a case at bakbone, lets see what those guys think...
Imho this has to be a bug...

@Those Guys with Netvault: what version are you running?
We run 8.2.1

[FBraendle]

Netvault support told me to get in contact with the drive manufacturer...
Lets see, there may be some firmware updates(though changes are slim at best that this will be addressed)

BTW:
I just checked the jobs which write our highly compressed Litespeed backups to tape(level 7), they have a ratio of 1:1 - 1.05:1
So this seems only to happen with the VBK files...
Weird thing: from what i can extrapolate from this posts here, it seems to be a Netvault error...

[dextr]

Has anyone gotten anywhere with this? I'm seeing 1:1 compression on a Quantum LTO5 drive when backing up our .vbk files to tape.

I'm thinking that since Veeam is already compressing the .vbk that the LTO5 cannot do any more to it.

[Gostev]

I'm thinking that since Veeam is already compressing the .vbk that the LTO5 cannot do any more to it.

Exactly.

[dextr]

Thank you Anton. Looks like we'll be ordering some more LTO5 media then!!

[tsightler]

I think the thread started because some users are seeing "reverse" compression (I guess that would be "expansion"), i.e. the VBK is actually taking more space on tape than on disk. I'd have to agree that this is probably some type of Netvault bug, although we don't see it with our Netvault install, we're pretty much right on 1:1 with only slight variation.

[isiman]

If the software is using software compression, it might be a bug, but doing it with hardware compression of tape drive, this could perhaps be a thing of "unfortunately mismatching" of blocksizes between disk and tape drive.

We are using LTO4 (block size 64 kB) and Symantec BE tells us a native tape size of 745 GB and data size of 781 to 788 GB (about 1,05:1). The 20 TB-Raid (with GPT) is formatted with 8 kB block size and Veeam is backing up with "optimal compression" and this seems to match...

isiman

[Matterdoit]

Been using Netvault to backup Veeam VBK files for a while now, tape is LTO4. Just checked both my backups servers 712.52 Gbytes, compression 1.006:1 server1 and 363.95, compression 1.011:1 server2. Did not think this was an issue before as I thought the VBK file were already compressed enough. I have checked the sizes of my vbk files and they match exactly to the size backed up to tape via Netvault, which would suggest no compression. No negative compression.