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Scheduling question

Scheduling question

Scheduling question

We're are hoping to go to a Enterprise Backup Solution soon, and Commvault is one of the products / vendors we are looking at.  We are questioning the full / synthetic full backups though.  When we first spoke to them they told us the first backup is a full, everything afterwards is incremental, then you make synthetic fulls.  When they gave their presentation to us, they showed a schedule of 1 day full, 6 days incremental.  I spoke to someone I know who just started using Commvault within the last 6 months and they do a full daily.  Why such discrepencies?  Is is just each sites preference?   

RE: Scheduling question

The synthetic fulls are handy for remote servers as you can use the previous backup that is stored locally to supply all the files that haven't changed leaving only the incrementals to traverse the wan link.

For local sites there is no reason to not use a full unless its for some other reason like the syth full is quicker cause its stored on better storage or the backup window isn't long enough to do a full from the source.


RE: Scheduling question

> Why such discrepencies? Is is just each sites preference?

It most certainly is just site preference. You can do fulls every day if you want, every hour if you want. Or you can do  fulls once a week, with incrementals every other day, or any other combination of fulls, incrementals and synthetic fulls. The choice is yours. The features are provided and you are free to use any of them when they suit you. In summary:

* A full backup backs up everything. It takes the longest to run and transfers the most amount of data. It can take a long time to complete, especially over a slow link, but the benefit is that it is a line in the sand - anything can be restored from it.

* An incremental backup only backs up what has changed since the last backup (full or incremental). This typically makes it very quick to run, as a typical site's data won't change that much on a day to day basis (depending on what that data is of course). To restore something later, you will need the incremental backup in question, PLUS the most recent full backup run before that, and possibly other incrementals (if any) between the two. So restores are a little more complex, but everything is protected and gee those backups run fast!

* A differential backup, which is like an incremental, but the subtle difference is that it backs up everything that has changed since the last FULL backup (as opposed to an incremental backup which backs up everything that has changed since the last FULL or INCREMENTAL backup). It means that differential backups start getting longer and longer each day you run them, but restores are easier than those run with incrementals instead.

* A "synthetic" full. Now this is neat! The concept is this: we know what's changed (ie. what an incremental or differential would pick up) and we already have the stuff that hasn't changed (it's on the last full backup), so why send the unchanged stuff again? We already have it! So a synthetic full backup runs an incremental backup and then COMBINES it will the unchanged files from the most recent full backup, and creates a NEW full backup! You get a new full backup but with only the pain of having to run an incremental. Neat huh?

I suggest you do some reading about fulls, incrementals and differentials, as they are a basic concept that you must understand before you start running any backup product. YOU need to decide which to run and when to suit YOUR site. Having conflicting advice from two different site is no reason to trigger alarm bells or questions here. In fact, I doubt you'd find two identical sites anywhere!

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