Deduplication expectations...
I'm trying to understand what I should expect from deduplication during the first backup of servers. For example let's say I back up a directory made up of Word documents, images, Excel spreadsheets, etc. Should I expect the first backup of that directory to have zero or a very small dedupe percentage? Another example. Let's say my first backup of another directory contains 3 SQL Server backups (not using SQL agent just backing up from disk SQL Server backups) which are full backups from 3 straight days. Therefore the data in the BAK files has changed a little but not a huge amount. Let's say each backup is 300MB. Therefore 3 files totally 900MB. Would my first time backup be around 900MB or would dedupe on that first backup cause maybe only 310MB for instance of space to be used in the dedupe folder.
I'm trying to understand are the advantages to dedupe really on subsequent backups of the same file except in cases like on a file server where multiple people have stored the same exact file in different directories. Therefore the first backup would be a bit smaller.
Thanks ahead of time.
First pass backups are dismal when it comes to dedupe ratios. I get compression rates better with tape drives!
Though, do a 2nd pass, and immediately, you'll notice a fantastic dedupe rate.
You could try and enable compression on the host too via the PDCONF file, and see what you get on top of the dedupe.. Though reporting on that metric will be difficult at best.
I will say I was extremely mislead by Symantec in faster backup times with dedupe... Far from it. Only EMC's Avamar seems to really make a dramatic difference in backup times, but we're comparing a Honda to a Ferrari (price, performance, everything..)