Compression

[frl]

Hello,

I know compression issue has been explained several times, also in the FAQ. I followed the instrucitons in the FAQ but still have problems.
I did a Quick erase and formated the tape, so the info for the tape is:
Blank Media
Device Information:
Group name GROUP0
Cartrige type DLT
Compression ON
Format type Fast seek
Block size 65536

So from the info I would assume that the compression is enabled. But still when the scheduled nightly backups occurs (we are backing up around 45GB of data to 40/80 dlt tape) it asks me "Please mount a blank media to continue the backup".
I would like to have all data on one tape to keep things simple. Data that we are backing up is not compressed, just user files (20GB) and lotus notes databases(25GB).

Thanks!

 

[TheLad]

What version of Arcserve and on what platform?

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"It's true, its damn true!"
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[frl]

Sorry,
ArcServe v9 on Windows2000 Server.

 

[davidmichel]

Sad but true that 45gb on a 40/80 tape means that compression is working. It very very very poor compression but it is working. So the question is why am I getting such a poor compression ratio and not why is it not compressing.

 

[frl]

Davidmichel, you are correct. I looked at the status window at the end of the backup when it asked me for another tape and it says:
Backup operation cancelled (because I didn't put another tape in)
2 Session(s).
2.703 Directories 31.768 Files (21.209,84 MB) Backed up to the Media.
270 Database(s)/Transaction Log(s) (22.833,96 MB) Backed up to the Media.
44.652,18 MB Written to Media.
Elapsed Time: 6h 2m 4s

So it did some compression but it was as you said very very poor. I know notes databases, .nsf files don't compress much, but at least the users files (which are mostly word,excel and powerpoint files) could compress better.

 

[davidmichel]

Yes, well some things to look for/consider:
Users might have enabled OS compression on their share.
The drive might be having soft write errors. These are recoverable errors, meaning that there was a failure to write but a retry on the next block worked. Result is poor throughput, lost space on tape, but no errors that would cause the job to fail. These should show up in the database under media view.
The brand tape. Manufactures all recommend specific brand/s and those really do work better.