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Old Hand
 
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Hall of Fame
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The speed of the backup is a good news. But I have couple of questions? Will it take less space in the tape drive due to compression? Will it be a reliable backup?
:)
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Old Hand
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Hi
On your 2 questions:
1) Space on Tape: if your tape device does compression on the fly as ours does. Our usual space saving is approx 65% when going onto tape.
This means that the 3.5GB file is stored on tape as 1.2GB - this is about 200MB more than the SQL 2008 Compressed backup.
If the original 3.5GB file is zipped using maximum compression then the ZIP file is approx 820MB (note: this maximum compression takes longer than the SQL 2008 Compression Backup)
So, this means that there is potentially 200MB that could be saved when storing onto tape for this 3.5GB database backup.
2) Reliability: because the SQL engine is doing the compression and not a third-party vendor, I am reasonably confident that this backup should be seen as reliable as the original .BAK without compression.
Thanks
Kevin
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SSC Rookie
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Hi,
and what about to restore? Do you need more additional space on disk to uncompress first?
Thanks in advance,
Prado
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Old Hand
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Hi
The "uncompress" actually happens inside the SQL Engine - so no additional space is required for a "temp" file. The only space required is the size of the Database and Transaction Log.
Note: If a backup file is 900MB - the actual size of the database Data file is 3.5GB and the Log 100MB - then this is the amount of space required on disk for the restored Database files (Data and Log)
Thanks
Kevin
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Ten Centuries
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Nice work Kevin!
The compress backups feature will come in handy in many environments - certainly will save space.
One question - I didn't see metrics for restoring. I'd be interested in seeing what the differentce in restore time would be for a compressed backup vs. non-compressed.
The reduced backup time was an interesting effect, it shows that the disk is probably the limiting factor in this instance.
Mark
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Hall of Fame
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Kevin (5/5/2008)
Hi
On your 2 questions:
1) Space on Tape: if your tape device does compression on the fly as ours does. Our usual space saving is approx 65% when going onto tape.
This means that the 3.5GB file is stored on tape as 1.2GB - this is about 200MB more than the SQL 2008 Compressed backup.
If the original 3.5GB file is zipped using maximum compression then the ZIP file is approx 820MB (note: this maximum compression takes longer than the SQL 2008 Compression Backup)
So, this means that there is potentially 200MB that could be saved when storing onto tape for this 3.5GB database backup.
2) Reliability: because the SQL engine is doing the compression and not a third-party vendor, I am reasonably confident that this backup should be seen as reliable as the original .BAK without compression.
Thanks
Kevin
Thanks Kevin on your prompt reply. This clears my doubt. :)
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Old Hand
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Yes, the restore from compressed .BAK file will be an interesting item to investigate.
I will get my environment up and running and either post feedback on this discussion or provide feedback in the form of a more in-depth technical article on the topic of Restore & Backups with SQL 2008.
Thanks
Kevin
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SSC Rookie
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Hi again,
A lot of thanks for your answer. Your explanations are very useful so we'll wait your feedback about the test for restore.
Thanks,
Prado
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SSCarpal Tunnel
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Thank you for highlighting this valuable feature.
Saving +60% is certainly worth investigating it to the bone, considering the vase amount of backup data we produce.
Nowadays we compress the backup by using disk compression at our safezone. (backups are procuded local and xcopied to safezone)
Won't compression on compression produce an overhead ?
 Don't drive faster than your guardian angel can fly ...
but keeping both feet on the ground won't get you anywhere 
Very usefull HowTo for forums:
- How to post Performance Problems
- How to post data/code to get the best help
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