Used capacity appear different to writed data used

[Steven_Giang]

Hi All,

I have been googling around til I couldn't actually yet find an answer and hope someone here could help out.

Please see attached photo, as you can see the media label as Monday-Wednesday and they used same backup job, selection and same media set.

The Monday tape actually a new tape I put in this week, however I couldn't understand the "used capacity" shown 823GB+ while the actual data (All Veeam compressed data) are 525GB only.

I go through the global setting as recommended on the forum here,

eg:

Encryption - this feature alway disable in the first day

hardware compress - was enable before, and after research there is not much use if the data has already compressed (which is Veeam backup data)

Could someone shed some light or maybe where should I look for in the log to identifies the extra tape space were used?

Thanks you,

Steve

[pkh · Accepted solution]

When you compress data which is already compressed, you are likely to end up with more data than what you have started with. Turning off hardware compression is a step in the right direction

[Steven_Giang]

Hi Pkh,

Do you know any supportive BE documentation regarding backup compressed data over compressed data?

I have another example (please see attached) the data are all Veeam compressed data, this job does not take up the capacity on tape. It used what it suppose to be.

Then this doesn't make sense to the job end up with more data than what I have started with above

[pkh]

There is no Veritas document for this because it is a well known compression fact.  You can read my article below for an explanation.

https://www.veritas.com/community/articles/compression-short-explanation