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Why in NBU same density of medias (say LTO4 800/1600 GB) write different amount of data ?

nbuno
Level 6

Why not same medias hold same amount of data always and why they gets FULL before actually the limit on their data has been reached..for example 2 media with 800/1600 GB capacity in NBU can write 700 1200 GB of data respectively and shows as FULL in NBU...thoughts ?

 

THANKS

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Accepted Solutions

sksujeet
Level 6
Partner Accredited Certified

Is it the same exact data that you are writing on 2 tapes? If not then If data is already compressed or if data is database files which can't be compressed much. If it is same data and showing this behaviour then we have to worry about though NBU is not responsible for it as NBU just sends the data to drives and its the hardware that does the compression for you.

Also are you using the compression and encryption witin NBU? Compression within NBU is not recommended and should be left to hardware. If the tape itself thiks that it is End of tape then it reports to NBU and there is nothing NBU can do about it. There might be sometimes corrupt medias which can't be used to full capacity.

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2 REPLIES 2

sksujeet
Level 6
Partner Accredited Certified

Is it the same exact data that you are writing on 2 tapes? If not then If data is already compressed or if data is database files which can't be compressed much. If it is same data and showing this behaviour then we have to worry about though NBU is not responsible for it as NBU just sends the data to drives and its the hardware that does the compression for you.

Also are you using the compression and encryption witin NBU? Compression within NBU is not recommended and should be left to hardware. If the tape itself thiks that it is End of tape then it reports to NBU and there is nothing NBU can do about it. There might be sometimes corrupt medias which can't be used to full capacity.

mph999
Level 6
Employee Accredited

Thoughts :

Don't use software compression (the tape drive hardware compression does a much better, and faster job)

Depends on how compressible the data is

If you write many many spearate tiny backups, the data is padded out to at least 512 bytes, so this would use a bit more tape than perhaps expected (not very likely that you are doing this)

Depneds also on drive firmware / faults

NBU has no understanding of tape capacity, a tape is only marked full when the tape drive firmware sets a 'tape full' flag in the tape drive sriver, which in turn tells NBU.

Martin