Using tape as a backup target
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JonJR
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Compression - is it working?

Post by JonJR »

Hey,

We recently moved our main file server from a Linux VM with ZFS LZ4 compression and a VM Snapshot Veeam backup. Now we have a Windows failover cluster with an uncompressed NTFS data volume protected by a Veeam Windows agent backup. Using a "Dell" ML3 LTO Tape Library, SAS connected to the backup server. Using a Linux XFS repo for the disk backup storage.

The old server had 29TB of data, the volume was 33TB and Veeam said it processed 33TB for the disk backup. When it went to tape, Veeam transferred 29TB and used 4xLTO8 tapes - so it all kinda made sense.

New server has 34TB Data, the volume is 60TB and Veeam says it processes 34TB for the agent (volume level backup). When it goes to tape, Veeam transferred 57TB and uses 5 x LTO8 tapes - so transferring ~20TB more than expected. Annoying for the extra tape and the extra 26 hours of backup time!

I have done one with compression "off" for the job and one with it "on" and it is the same amount transferred regardless. We do have Inline data reduction and "optimal compression" on. The logs for the backup job show "Job Options: 'Hardware Compression: True" and I can't see any other errors for the job.

I don't expect to get 2:1 compression as promised by LTO, but I also don't expect the tape backup to be bigger than the source data. Surely it's not copying the empty space to disk? Am I doing something stupidly wrong here? Is there a way of seeing what's happening?

Thanks Jon

JonJR
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Re: Compression - is it working?

Post by JonJR »

Also no encryption anywhere in the processes and the TapeHost.log says: ----------Drive params---------- Compression: true

HannesK
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Re: Compression - is it working?

Post by HannesK »

Hello,
if the backups are compressed with Veeam, then enabling tape compression has little to zero impact.
processes 34TB for the agent (volume level backup). When it goes to tape, Veeam transferred 57TB
how much data is stored on disk? Is it just one full backup, or also incremental backups? The "transferred" value... is that for the backup job, or for the tape job? The value should be the same for the backup job and the tape job. If not, what did support say about that (case number)?

Best regards,
Hannes

JonJR
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Re: Compression - is it working?

Post by JonJR »

how much data is stored on disk? Is it just one full backup, or also incremental backups? The "transferred" value... is that for the backup job, or for the tape job? The value should be the same for the backup job and the tape job. If not, what did support say about that (case number)?
It's doing the tape backup from a preceding synth full agent backup. The agent backup is processing 34.TB and transferring varying amounts whereas the tape job is processing and transferring 58TB.

Just opened support case #05473850

HannesK
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Re: Compression - is it working?

Post by HannesK »

Hello,
after checking the screenshots in the case, I just realized that you are backing up a failover cluster (as mentioned by you, but looks like I did not notice it)

The backup to tape job duplicates the data, because the cluster has two nodes. While not nice, that's how it works today. A workaround could be to use file-to-tape.

Best regards,
Hannes

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