And another question, just as important: do you know what you backup?
To those who do know, the question may seem trivial--even insulting. Of course I know! But do you? Really?
Two recent cases make me think that some backup admins who think they know how much they are backing up, in fact, don't know.
Sort of a case of however much you think you are backing up I do not think you are backing up what you think you are backing up.
In each of these cases, the backup admin was off by about a factor of 3. One thought he was backing up about 1.5 TB per day. It is actually 4.7 TB per day (and climbing). Another was convinced that he was backing up about 2 TB per day. In that case, he actually backs up about 7 TB per day.
I think there are two important issues here. First is the obvious one: how much is this going to cost you? Clearly you need more capacity to back up 7 TB per day than you require to back up 2 TB per day. More disk, more tape, more network, more bandwidth, just more infrastructure in general.
The second issue is one of what all that extra data is. In one of these cases above, we found out that a bunch of snap shots of a database were being backed up inadvertently. The database got backed up everyday at midnight, and then another 3 copies were captured throughout the day. In addition to log files. And there was no SLA to do database backups more than once per day. So basically, about 1.5TB of data was being backed up every day, and being retained for 3 months, that was completely superfluous and unnecessary. Hrmm. Not good.
So what to do about this? Well, from a self-interested point of view, I would recommend that you engage an EMC backup expert to help you conduct a backup assessment before any backup infrastructure upgrades. This assessment can be done on pretty much any and every major backup application, and will help identify how much data is really being backed up.
It can also identify what kinds of data, from what clients, and identify common failures in the backup environment. It can also identify data which is suitable for archiving, and how much of it you have. This is critical as it may represent a way to help you avoid growing your backup environment entirely: if you can archive 40% of your data, that is 40% less that you have to back up. How much longer would your backup infrastructure be good for if you could reduce the load on it by 40%.
Failing that, there are other services and methods to assess the size of your backups, and the types of data within them. If nothing else, some such method should be employed before any upgrade. It is always better to know that you are backing up 7 TB, not just 2 TB, before you attempt an upgrade!