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HP Ultrium LTO Compression Ratio

Lisa Garczynski
Occasional Contributor

HP Ultrium LTO Compression Ratio

We are backing up SAP / Oracle databases using HP Omniback. The largest database is currently 250 GB. We are using DLT 7000 tape drives and can fit 130 GB on one tape. The database has about 20% of free space.

We are trying to size the number of slots we need for an LTO tape library. Using 2:1 compression we should need 3 tapes, but in our current environment we are only using 2 per backup.

Does anyone else have experience with this type of enviornment? Our operating system is HP-UX 11.0 and backup software is OmniBack 3.5. We are using hardware compression only.

Thanks for your help.
Regards,
Lisa
5 REPLIES
Vincent Fleming
Honored Contributor

Re: HP Ultrium LTO Compression Ratio

Hi Lisa,

I'm not sure exactly what you're asking... so, here's some general info:

You are using 2 tapes now. I would think that 2 drives would do you well, if you are meeting your backup window. If you are concerned about the future needing more tapes, be sure to get a library that can be expanded to handle more drives. For example, s 4/40 library with 2 drives in it would allow you to add 2 drives in the future.

If you are tight on your backup window (ie: you are allowed 2 hours, and are now taking 1.75 hours) and are concerned about running long, get 3 drives or more, which will reduce your backup time.

I hope this helps. Good luck!
No matter where you go, there you are.

Re: HP Ultrium LTO Compression Ratio

Hi,

Yes, what are you saying is true. You could fit
130 GB of SAP/Oracle DB using DLT-7000 drive in one DLT4 tape.

On LTO tape with 2:1 compresion rate count on 240GB of data/tape, so you need only two LTO tapes to do your backup. Be sure that you use LTO 230 drives.

MB
Eric de Lange_2
Respected Contributor

Re: HP Ultrium LTO Compression Ratio

Thoughts,

The advertized compression ratio for a DLT7000 is 2:1 as well.

Currently you are storing 130GB on a 35GB tape. This calculates into a compression ratio of 3.7:1

Since the compression ratio (i.e. the ease with which data can be compressed by the hardware compression chip) is largely dependant on the type of data, it would be safe to assume that the Ultrium drive would give you the same behavior.

This means that technically you would be able to store about 370GB on an Ultrium tape with HW compression. This means your whole database would fit on a tape.

Still, I would allocate 3 or 4 tapes for it as it to cover for emergencies, copies, etc.

have a good weekend.

-Eric
Lisa Garczynski
Occasional Contributor

Re: HP Ultrium LTO Compression Ratio

Thanks for your replies.

The reason I am asking these questions is the amount of data on a tape will determine the total number of slots needed in the library and the number of tapes used needed. The 'advertised' amount of compressed data that can fit on one DLT4 tape is 70 GB. We are getting almost twice that amount per tape.

If we get the same 3.7:1 compression ratio on an LTO tape then we will need 7 tapes per week until the database is 370 GB. If we get 200 GB per tape (as advertised) then we would need 14 tapes immediately and three when the database is over 400 GB. We are trying to size the library for 3 years of growth so there is a big difference in the library size depending on the amount of data that can be stored per tape and number of tape slots required as a result.

We are attempting to borrow an LTO tape drive to do a backup test using our data.

Thanks again for your help. Have a good weekend.
Lisa
Leif Halvarsson_2
Honored Contributor

Re: HP Ultrium LTO Compression Ratio

Hi
I use a LTO library to back up Oracle databases
( with OmniBack 4.1).
At first, you can expect the same compression ratio with a LTO drive as with DLT. LTO and DLT drives use the same compression algoritm (LZW).

The compression ratio 2-1 is approximative and depend of the data you backup. For example with plain text files you can expect a 2-1 ratio. Database files often contains mutch "empty space" and you can gett a better ratio. On the other hand, files from some "computational programs" (FEM,CFD) will not give a better ratio then 1.3-1 or so.