45GB data on DDS3 drive

[Sunil Kumar K.U.]

Hello All,

I have a customer who has aroung 45GB of data to be backed up on a DDS3 drive connected to a HP9000/L1000 server. Currently they are taking backup on 2 DDS3 cartridges. Is there any compressing utility available on HP-UX so that these files can be compressed first and then backed up to the tape? The idea is to include the full backup on a single DDS3 tape.

pls. note that currently the backup is taken with compression using appropriate device files.

If anybody can throw some light on it?

Thanks in advance
Sunil Kumar

[Thierry Poels_1]

Hi,

I presume that 45GB for one DDS3 tape is not feasable. It depends on the data tough; if the data is megacompressable it might be possible, but chances are low.
Gzip could be used to compress files before backup.
So:
- more than one tape
- upgrade to DDS4, DLT, ...
- add a drive
- selective backup
- ...

good luck,
Thierry.

[Darrell Allen]

Hi Sunil,

The tape drive is providing compression which is probably better than what you can achieve with software. DDS3 capacity is 12GB uncompressed data and 24GB compressed. That assumes a 2:1 compression ratio which is not likely.

Darrell

[Sanjay_6]

Hi Sunil,

The maximum storage capacity of a DDS3 Drive is 12/24. 12 GB in native mode and 24 GB in compressed mode. I don't think you can take backup of 45 GB of data on a single DDS3 drive. You can look for some compression tool that can compress the data such that it can fit on one tape but that is doubtful. Good luck. Maybe someone else can help you.

Regds

[A. Clay Stephenson · Accepted solution]

Hi:

When planning you should only rely on the uncompressed capacity of the medium; 12GB in this case. While it is possible, that this medium could hold 45GB is is very,very unlikely. Pre-compressing the data and then sending that data-stream to a hardware compression device will actually expand the data a bit. You should choose software compression and no hardware compression OR hardware compression and no software compression but not both. Generally the only time software compression makes sense is when you need to send data over a rather slow network to a remote backup device. If you want to put this much data on a single medium then you should really look at DLT or Ultrium devices whose native capacities are near your desired value.

Regards, Clay

[Helen French]

Hi Sunil Kumar K. U. =)),

Few things for ur help:

1)Although there is nothing wrong with using Hardware compression along with Software compression, typically there is no advantage by using hardware compression when using software compression as well.

2) For software compression (on backup), you can use Omniback, Legato or gzip utilities. But, If data is compressed regardless of the utility (Omniback,legato, gzip,etc???) before it is received by the Tape Drive, additional compression by the hardware is unlikely.

3)Check this out for eg:

http://us-support.external.hp.com/cki/bin/doc.pl/sid=0629bd1a16b1cf5bdc/screen=ckiDisplayDocument?docId=200000058096829

HTH,
Shiju

[Bill Hassell]

In general, the compression ratio does not vary a significant amount between the various compression methods. If you compress the data in software, then pass it to the tape drive, the hardware will find almost nothing to compress so there is no advantage.

In general, it is not a good practice to assume 2:1 compression will be the norm. The ONLY value that is guarenteed is the native capacity. So the DDS3 tape will indeed backup 12Gb...anything more is a bonus and 100% dependent on the content of the data, something you can't control.

Even the DDS4 tape drive will not help as the native capacity is only 20 Gb. To fit everything on one tape, you'll have to replace the tape drive with something large enough for your data, perhaps a DLT 8000 which has a 40 Gb native capacity. That is close enough to your 45 Gb to make sure it always fits, but if your data requirements grow (they usually do), you may outgrow even the single tape DLT capacity.

So I would recommend adding another DDS3 drive and use fbackup's built-in capability to access multiple tapes in the same backup. However, for long term planning, I would recommend a 6-tape changer. That way, a DDS3 changer will accomodate 72 Gb native capacity and probably more than 100 Gb with compression. fbackup can accomodate a tape changer with an appropriate chgvol script.

[harry d brown jr]

Sunil,

Look into either DLT, or better yet, a stacker (either DLT or DDS).


live free or die
harry

[Sunil Kumar K.U.]

Hello all,

Thanks for the detailed and quick response. I suggested a DLT8000 drive since his data growth is very less.


Regards
Sunil Kumar K.U.