Re: OmniBack II, DLT4000 - other Backup Issues

:> Hi,
:>
:> We are building a data warehouse on a HP9000 (HP-UX 10.2) box using
:> Oracle 7.3 as the backend database server. Our hardware vendor has
:> recommended to buy OmniBack II and DLT4000 5 Catridge Autochanger for
:> our backup and recovery requirements.
:>
:> The database will be about 100 GB in size with nightly loads from DB2 to
:> Oracle. The database will backed up every day. There will be incremental
:> backups of root and other OS file systems and weekly complete backups. I
:> would like to know your opinion on the following:
:>
:> + It is well known that OmniBack is faster compared to SAM Backup &
:> Recovery (SAM B&R). Which of these two are better to use in my
:> environment? We have no plans now to use OmniBack for anything other
:> than backing up the UNIX system.
:>
:> + Do we need DLT4000 5 Catridge autochanger, which is an expensive
:> product, compared to a simple DLT4000 desktop tape drive that allows
:> only one tape at a time.
:>
:> + We were told that backing up using SAM B&R will make backups slower
:> and the tapes can hold only 16 GB/tape compared to OmniBack II which can
:> hold up to 40 GB/tape.
:>
:> Any opinions, suggestions or comments are appreciated.
   

        A few questions:  

1. Are you planning on doing Cold or Hot backups?
2. Do you have a backup window you are hoping to fit inside off?

You definately cannot just get a single DLT-4000 unit, unless you want to come in every night and change tapes. With 2:1 compression the best you can fit on a DLT-4000 tape is 40GB. You'll need two and a half of these tapes for your 100GB database.  

        I do a weekly cold back up of my Oracle Database to a DLT-4000 tape drive. My server is a SPARC 20 with a 200MHZ HyperSparc processor running SunOS 4.1.4.  

        To backup 20GB of diskspace takes me a little over 4 hours with the DLT-4000 using the standard dump and restore commands. I would expect your 100GB to take approximately 20 hours with a DLT-4000 from my experience.  

        In that case I WOULD NOT recommend a 5 tape autochanger for your situation. Instead, I would recommend two DLT-7000 tape drives. Each drive can hold 35GB native capacity, 70GB with 2:1 compression.  

        The problem with the autochanger is that you can only write serially (one tape after another) Which means if it takes 4 hours to write a tape and you need 5 tapes to do a complete backup, its going to take 20 hours.  

        The DLT-7000 drives are quite a bit faster than the DLT-4000 tape drives, If you can keep them in a streaming mode. (The DLT-7000 is rated at 5 Mb/s vs 1.5 Mb/s for the DLT-4000)  

        With two drives running simultaneously (perhaps on two seperate SCSI buses) you should be able to backup all 100GB in a reasonable amount of time. I'd estimate: 3.5 hrs.  

I'm estimating the 3.5 hours by saying:  

100GB sent to two tape drives (50GB to each drive) (in parallel)  

50GB backed up at 5 MB/s = 2.78 Hours.
But, I don't have experience with the DLT-7000 yet, so I don't quite trust the 5MB/s rating. (I am in the process of purchasing a DLT-7000 unit) I'd guess more 4MB/s which gives:  

50GB at 4 MB/s = 3.47 Hours.    

If it really is a requirment for your site that you backup all of the database, nightly. You may want to look into one of the higher end tape units sold by someone like Cybernetics, but they are going to cost you.  

As for the OmniBackII software. I personally don't think something like this is needed for a database server. Databases consist of very few large files (in general) not many, smaller files (such as user home directories)  

In the case of a file server or User home server, something like the OmniBack software may help to increase speed, due to caching, etc. But for a database I'd think the basic Dump and Restore commands would suffice.  

Good Luck,  

Al

-- 
Al Dorrington                               awdorrin_at_ictest.delcoelect.com 
Delco Electronics - IC CIM                  Database & Unix Administrator
Kokomo, Indiana, USA                        Phone: 765.451.9655