Can My Lto3 tape be filled up to 1.6T a tape?

[lamp_box]

I have check the media with the available_media script, but

i am really confused with my result:

there are some parts of what i getted:

media   media        robot   robot       robot      side/         ret      size                  status
ID          type             type   #               slot       face         level     KBytes
D204L3 HCART3   TLD      0              33          -                3     159771883       ACTIVE
D203L3 HCART3   TLD      0              32          -                3     232473             ACTIVE
D226L3 HCART3   NONE   -               -            -                3     1556956683     ACTIVE
D212L3 HCART3   TLD      0              36          -                3     1634539937     FROZEN

the tape D226 and D212 all encounted some write error when i am having some backup job. I have to move the D226 out the library manually and freeze the D212.

But in this check, i found the tape size is up to 1.5 T AND 1.6T in the two tapes!

is this really normal?( without compress option)

btw, the reading of the two tapes is just all right.

 Can anyone offer any help/clues?

Message Edited by lamp.box on 01-31-2008 02:08 AM

[Darren_Dunham]

With compression on (the default), that is possible.

The only way to be completely certain is to read the data from the tape and see how much is on it.

--
Darren

[Chuck_Stevens]

I thought LTO3 maxxed out at 800 GB fully compressed?

[Tom_Burrell]

Well that's the rated number, but your actual compression rate may be different depending on your data.

I've seen higher than 2:1, but 4:1?? Something doesn't seem right there.

[Darren_Dunham]

---

@Chuck Stevens #2 wrote:

I thought LTO3 maxxed out at 800 GB fully compressed?

---

No, that's only a planning figure.  Compression ratios depend on the data itself. 

For instance, I've often had DBAs that had pre-allocated tablespaces on disk, but they were mainly empty (lots and lots of zeros).  Those got excellent ratios.  Without knowledge of the data, there's no way to know if 4:1 is likely or a sign of a serious problem.

If he says it's a disk full of JPG/MPG image data, then that wouldn't be good.  :)

--
Darren

[Stumpr2]

Let me put my amen to Darren's post.

Does that help?  j/k  LOL

[Chuck_Stevens]

Well, I've learned something today, and that means I can go home.  Thanks! 

[Stumpr2]

---

Chuck Stevens #2 wrote:

Well, I've learned something today, and that means I can go home.  Thanks! 

---

aw' man! That's not fair. I work from home. I guess can go to my Lay-Z-Boy.

[lamp_box]

thank Bob,Stevens and Darren and Tom.

I 'd like further  describe my condition as follows : 
1) the policy is for a standard backup not for database, and is not compressed.

The point is that: the data are not compressed!

Policy Name:       A_product

  Policy Type:         Standard
  Active:              yes
  Client Compress:     no
  Follow NFS Mounts:   no
  Cross Mount Points:  no
  Collect TIR info:    no
  Block Incremental:   no
  Mult. Data Streams:  no
  Client Encrypt:      no
  Checkpoint:          no
  Policy Priority:     0
  Max Jobs/Policy:     Unlimited
  Disaster Recovery:   0
  Collect BMR info:    no
  Residence:           Product-hcart3-robot-tld-0
  Volume Pool:         Product
  Keyword:             (none specified)

2) the data can be read, we have done a lot restore test.

of causte i havent tested all the images in the tape, but the latest images should be all right.

3) all the tape will encounted an error when the size reached such tremendous SIZE.

4) the error is "- Error bptm(pid=66645) close error on media id D226L3, drive index 2, No CSI structure

available. (bptm.c.18123)
- Error bpbrm from client Product: ERR - bpbkar exiting because backup is aborting  
- end writing; write time: 00:19:49
media close error(87)"

any further suggestion???

Message Edited by lamp.box on 01-31-2008 07:50 PM

Message Edited by lamp.box on 01-31-2008 08:02 PM

Message Edited by lamp.box on 01-31-2008 08:21 PM

Message Edited by lamp.box on 01-31-2008 08:24 PM

[ahlip]

I believe that the guys here are refering to hardware compression occuring realtime at the tape drive. Typically this can give tremendous compression for data types like padded database files. I have seen before 4:1 compression on Oracle data on LTO-1.

But if you are getting an error, then it is something you should escalate to NetBackup support.

[sshagent]

yeah as above...its drive hardware compression that is doing it.  I remember back in the day getting some monstrous amount of gb's on a DLT tape...cos of backing up some massive oracle db ( that was empty - and thus very compressable(new word?)

[lamp_box]

Hardware compression? how can i make sure it, anyway to test it?

It seems like my tape can't change the status to the FULL . and i am sure i have't use the DISALLOW_BACKUPS_SPANNING_MEDIA entry on bp.conf. i will monitor the tape until one of them become FULL. otherwise there must be some configuration errors.

[Srikanth_Gubbal]

Hi,

in addtion to all the suggestion added, let  me add some more information

by default hardware compression is enabled for all the next generation tape drives.

best compression scenerio is

Files that are composed of the strings that repeat can sometimes be compressed to 1% of their original size.

NetBackup does not compress the following files:
■
Files that are equal to or less than 512 bytes, because that is the tar block size.
■
On UNIX clients, the files that end with suffixes specified with the
COMPRESS_SUFFIX =.suffix option in the bp.conf file.
■ On UNIX clients, files with the following suffixes:
.arcor .ARC,.gzor,GZ,.iffor .IFF,.sit.binor,.arjor .ARJ,.hqxor .HQX,.pitor .PIT,.SIT.bin,

.auor .AU,.hqx.binor.pit.binor.tiffor .TIFF.cptor.CPT.HQX.BIN.PIT.BIN.Y.cpt.binor.jpegor .JPEG.scfor

.SCF.zipor .ZIP.CPT.BIN.jpgor .JPG.seaor .SEA.zomor .ZOM.F.lhaor .LHA.sea.binor.zooor .ZOO.F3B

.lzh.SEA.BIN.zor .Z.gifor .GIF.pakor .PAK.sitor .SIT

so, compression is based on the type of data, try to analyze the data you are backing up.

regards,

SriKanth.

[Chuck_Stevens]

Also note that, from my experience, data that has been encrypted via the Media Server Encryption Option will not be compressed by the tape drive hardware.  To get it to compress, you have to configure MSEO to do it for you.