Chris has comments on the DL 6000 series, lets watch.
So, you'd need 1.5 Copan devices to match the EMC kit and yes, it doesn't scale as well in terms of virtual components, but there are some big issues here. For instance, EMC's device isn't green - the power demands are huge and not surprising, as the drives are all spinning all the time (Copan have only 25% max if theirs in use at any time).
Oh bloody hell, where's my backup & recovery cap and someone page the Cap'n as I'll need him in a moment.
Right, lets take the green comment first. When it comes to power the 6000 series isn't limited by the fact that it can rotate all the rust at once it's limited by the fact that at the moment it can't spin down the rust which hasn't been used in a while. Copan's box on the other hand is limited by the fact that it can only rotate 25% of the rust at any one time. So in a DR situation you're waiting for disks to come online, only to watch others spin down when you hit the 25% limit. Think of how this affects an incremental forever BU product like TSM. Unless you've been colocating like crazy you could touch every LUN in the system for a restore operation depending on where the virtual carts are located but you can only access 25% of them at any on time.
Someone might ask "But how often would you really require a DR size restore?", the answer to that question is that you only need to have to do it once to see how much of a pain in the ass waiting for disks to spin up and down will be. It'll be faster than loading and unloading tapes but you've needlessly hamstrung yourself.
People think that VTLs are only about solving backup performance issues. They're not. They bring greater value to recovery as you don't have to trade backup performance for recovery performance. What are you doing when you're only powering 25% of your box? You're trading recovery performance for lower power utilization and if you're going to do that you can do it a hell of a lot cheaper by just using tape.
Here comes the Cap'n..
Captain Obvious says:
Backing things up quickly to tape was solved years ago, the answer is in multiplexing backup streams in order to keep tape drives running in burst mode. The trade off of course was the fact that recovery performance of multiplexed save sets is atrocious and positioning intensive. If you're looking for fast backup and want to be green then tape with multiplexed save sets is as green as it gets, if you want fast recovery then you'll want Backup to Disk or VTL technology. Keep your operational backup and recovery data on there for 30/60/90/180 days and then shove it off to tape. VTLs are rapid recovery devices which are non-disruptive to a tape based management infrastructure.
The next paragraph nearly had me storming the castle with pitchforks and burning torches.
Floor density is not good in the DMX - why? Because the drives are in use all the time and it is an Enterprise array, so timely replacement of disk failures is important - but less so for a virtual tape system which can tolerate downtime.
No they can't tolerate downtime. VTLs are designed to facilitate always available high speed recoveries, if someone can tolerate downtime I say again look at tape as they obviously don't have the requirement for a VTL. Throw an Advanced File Type Device or disk pool up front and then stage off to tape and you'll be set. You'll also reduce your power requirement substantially by moving recovery of data a few weeks old to offline media. Restore is going to be slow (The take a few days off kind of slow depending on the amount of data) and a general pain in the ass as tape juggling always is but you are robbing Peter to pay Paul after all.
Backup & Recovery is the last line of defense against all the nasty things out there and yet we read stories about backup & recovery incompetence every few weeks because someone thought that backup maintenance was a lower priority task. It's not. These are the systems you use to mitigate the effects of other peoples stupidity and acts of god.
If that isn't a high priority gig then I don't know what is.