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Enabling Native Tape Drive Compression on LTO5 and LTO6 Drives

Created: 14 Jun 2013 • Updated: 16 Jun 2013 | 7 comments
This issue has been solved. See solution.

Does anyone have a walk through on enabling tape drive compression(NOT software compression)?  I've been doing some research and it appears commands such as: sdparm - <device>, and sginfo -a displays the following information:

Data compression (SSC) mode page:
  DCE         1  [cha: y, def:  1, sav:  1]
  DCC         1  [cha: n, def:  1, sav:  1]
  DDE         1  [cha: n, def:  1, sav:  1]
  RED         0  [cha: n, def:  0, sav:  0]
  COMPR_A   255  [cha: n, def:255, sav:255]
  DCOMPR_A  255  [cha: n, def:255, sav:255]
I have 6 Netbackup 5200 and 5220s connected to an IBM3584 with 12 LTO4, 5, and 6 drives via FC.  The library and drives are functioning however, I'm not getting no where near the data compression on the LTO6 tapes that I thought I would.  I'm only seeing about 3.1TB on a LTO6 tape.
Can someone explain the output above and what my settings should be.  Thanks.
Operating Systems:

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Nicolai's picture

A LTO tape drive will always compress the data. The native capacity of LTO6 is 2.5TB per and you are seeing 3.1 TB per tape so the tape drive do compress data.

The 6.25TB per tape is based on a compression ration of 2.5:1. 

See :

Assumption is the mother of all mess ups.

If this post answered your'e qustion -  Please mark as a soloution.

WorrelM's picture

Something is not adding up. According to my activity monitor I'm getting better compression on my LTO4 tapes and my LTO6 tapes. How can this be?

Media ID Barcode Media Ty pe Robot Type Kilobytes Robot Number
----------- --------- ---------- ----- ------------- ----------- -----------------
BL4489 BL4489L4 HCART TLD 3215266120 0
BL4212 BL4212L4 HCART TLD 3243377209 0
BL6078 BL6078L6 HCART3 TLD 3375762173 0
BL4165 BL4165L4 HCART TLD 3379368235 0
BL6077 BL6077L6 HCART3 TLD 3379436821 0
BL6075 BL6075L6 HCART3 TLD 3382133218 0
BL4168 BL4168L4 HCART TLD 3554453846 0
BL4284 BL4284L4 HCART TLD 3789729646 0

StefanosM's picture

are you backing up the same data to both tapes?

as nicolai write, tape compression is always enabled. try to do a test.

Create a new policy and add a big client to the policy.  Be sour that the client files are compressible (no photos).
Point the storage unit to the LTO4 drives. Use a new volume  pool.
start the policy several time until the tape is full.
Do the same with an LTO6 volume pool.

Then compare both tapes.

WorrelM's picture

Ok but how am I getting over 3TB on a single LTO4 tape??? The drive must be compressing over 2:1.

Marianne's picture

It all depends on compressibility of your data. Some compress better than others.

I believe that Nicolai has answered your question - no need to enable compression, it is enabled by default.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
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WorrelM's picture

Well, I found a utility from IBM called the IBM Tape Diagnostics Tool that I can use to gather information about the tape drives. I'll see what I can get out of the tool. Thanks.

Marianne's picture

Please remember to mark Nicolai's post as Solution.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links