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Compression Ratio with Backup Exec

Posted on 2004-10-14
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I am running Backup Exec 9.1 on a PIV, 1.5 GHz, 512 MB RAM. I am backing up about 14.0 GB of data. Tape drive is a Seagate 20/40. Tapes I am currently using are 12/24. The compression ratio I am getting is 1.08:1, which in my opinion, sucks! I am backing up 13.3 GB on 1st tape, and 700 MB on 2nd tape.

I am currently trying to test whether Hardware or Software compress gives me a better rate, but I was told that because our files are CAD files primarily, compression on the drive won't help much. Is this true? Any ideas?

I do daily backups, so I would hate to have to use 2 tapes per day, so if the compression ratio is average for CAD files, I guess going to a 20/40 tape. Once I get over 20 GB, it's time to change drives??? Thanks.

James
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Question by:stressbuny
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by:Lee W, MVP
ID: 12309573
Compression depends entirely on the file type.  Database files tend to compress greatly.  JPGs and MPGs compress VERY poorly.  Further, to maintain throughput, systems will not do HIGH compression, but rather fast compression.  Take a few of your CAD files and zip them.  What's the compression ratio?  If it's 1.25:1, I'd expect around 1.1-1.15:1 through tape compression.

I NEVER plan my backup system around advertised compression rates.  It's just a bad idea for the reasons you're experiencing.  I use to back up a VARIETY of files - 600 GB - and I got about 125-135 GB per 110 native/220 compressed SDLT tape drive.  IGNORE advertised compression unless you're backing up a database.

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by:Lee W, MVP
ID: 12309583
DLT or better still SDLT holds much more data.  LTO as well.  Current formats of LTO and SDLT hold at least 160GB of data per tape.  Over the long run, depending on your backup scheme, these tend to be more efficient, effective solutions.

What's your backup plan like?  Fulls and Differentials?
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by:stressbuny
ID: 12309621
I checked several CAD files, and my compression ratio on those files is about 1.3125:1, so I guess this my issue, I appear to be hitting the upper threshold of what the software/hardware can compress based on file types. I also have a good amount of JPG and TIF files, as well as long file names.

I guess as a rule of thumb, with my file types, I should not assume compression is going to help at all, and base my backup solution on this.
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Author Comment

by:stressbuny
ID: 12309645
My schedule is:

Full backups M-F, running at night. I keep every Thursday tape (earmarked as a Weekly Backup) for 4 weeks. Every month I do a monthly full backup and take off-site. Probably a bit of overkill, but that is my scheme that I have in place. at this time.
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by:Lee W, MVP
ID: 12309677
Nightly fulls strike me as overkill, yes.  I'd recommend weekend fulls, and a differential every night.  Use 1-2 tapes for the full (as needed) and the differentials will probably fit on 1 tape for the week.  Save you a lot of tapes doing it that way and you are pretty much as secure as if you were doing nightly fulls.  Restores just take a little longer if the whole system goes down.  Otherwise, they might be a little faster because you don't have to search through the entire tape for a file (if it's been changed).
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by:stressbuny
ID: 12309736
I know it's a bit of overkill, but the company I am working for is not very "network" savvy, so I have to do restores of files rather often. I think I may see about switching to a 20/40 Tape, and seeing if the boss bites on that. When I started here, there was NO backup whatsoever; everyone was "responsible" for their own drives, though they had a file server.

Thanks for the help on this one, I have been pulling my hair out for weeks, thinking there was something wrong with the drive or the software. Swapped out the drive under warranty, upgraded software, reinstalled windows, etc. Compression ratios should be given a better description as to advertising.

I will look at DLT or SDLT later, once we exceed capacity. We have only added about 2 GB of data in 3 years.
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Lee W, MVP earned 20 total points
ID: 12309771
Another suggestion - consider getting a Windows 2003 server as their file server and using Volume Shadow Copy - I implemented that at my current position and it's helped quickly recover files on two occasions in the last month or so.
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Author Comment

by:stressbuny
ID: 12309802
Yeah, company probably doesn't want to spend the cash. Had to pull tooth and nail to get SBS 2000 server; old server was a Win98 file server. Didn't even have DSL when I got here, was using a dial-up AOL account. Even though we are running SBS 2000 with Exchange now, it's on a PC, not a RAID machine. We only have 10 employees, so the system we have in place is 100 times better than when I started.

Thanks for all the help. I am trying to run my backup with Hardware only and Software only to see if one does better at compression than the other. If neither works, probably going to switch tape capacity till that is exceeded.
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by:Lee W, MVP
ID: 12310058
Could be wrong, but I think if the backup software detects hardware compression, it disables software compression.
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