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D2D disk space computation, Exchange

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Hey there, everyone -


I tried searching for the answer to this before posting, but nothing came up that directly and exactly answered what I'm trying to get at, although there were some insightful comments here and there...


I need to backup an Exchange system (both database and individual mailboxes) to a SAN, and I need to estimate the disk space requirements so I can allocate enough on the SAN for this purpose without wasting too much space. I need full backups daily, and the ability to restore from disk (at minimum!) every day for the last week and one day a week for the past month. Grooming will be enabled and set at the default Retrospect policy. Incidentally, we will snapshot to tape weekly, but that's beyond the scope of my question here.


I understand the "set aside 2x the disk space for proactive backups" for files, but does the same apply for Exchange databases and mailboxes? Previous posts I found in this forum suggest that the disk usage for D2D by the Exchange agent may not scale the same way file backups do (probably something to do with the way Retrospect does matching) - and this uncertainty is exactly what I'd like to get an absolute answer for.


In short, does matching apply to Exchange databases and mailboxes?


My Exchange data is about 40GB, and grows at about 50MB per day... so using the proactive backup with a full backup daily assuming the needs stated above, do I need to set aside 160GB (2x 40GB for mailboxes plus 40GB for database) on the SAN for this data, or 880GB ( (7 daily + 4 weekly) x 80GB )?

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  • 3 weeks later...

Matching applies to mailboxes but not to databases. Exchange Database backup is done through the Microsoft API's and the size is dependent on the type of backup you choose (Full, Differential or Log) and the amount of data that is changing. Full will backup the entire database every time. Differential will backup the changes since the last Full backup. Log will backup the changes since the last Log backup.

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