Hi Optimus,

It's a built-in feature for a lot of backup software, not just for Backup Exec.
My pro's and cons would be as follows:

Pro's
1. Useful area for staging big backups to disk before duplicating to tape - this would cut down on a lot of time initially taken to back up to tape.
2. Additional storage for restores, or data that can be archived to a disk.
3. Fall-back device if your tape device fails - you'll be able to redirect to disk while it's being sorted out.

Cons
1. HDD failure - you will lose everything on the drive
2. USB time-outs - this would stop your backups (same with a SCSI time-out with a tape drive)

If you can leverage B2D and tape, I would recommend it. I am waiting for additional storage for our EVA 6100 to do the exact same thing.
To answer your last question, if it's an external disk (as in attached by a cable), it would be a removable B2D.

Laters!

Hello Optimus,

if you don't have a tape device attached to your backup server (so you can setup some b2d to tape jobs) and tape library is too expensive for you to buy it, at least buy some kind net disk case which support mirroring... it is very small chance that both of disks in mirorring will die at the same time :)

But then again you shoud chekc your company data security polici to see recomendations for bacukup environment.

Regards,
Marinko

Hello Optimus

Backup to Disk is a probably much slower backup than to a tape; in our environment (backing up to a separate raid with 8 disks) it is not half as fast as one tape drive. 

Also disk fragmentation needs to be cared for.

Regards,
Patrick

Hey Optimus,

I don't think it really matters if it's on the HCL in this case. It would be attached via USB. TO my knowledge, there is no best practice around what specific hardware to use...this depends on your budget. I am lucky that I have an EVA 6100 at my disposal. Otherwise a normal USB-attached HDD would have been what I would have used.
Speaking from experience, duplicating to disk fpr GRT restores is quite quick, and I use this all the time. This includes to some of the site server local disks when need be.

1TB Western Digital Caviar Green (SATA Hard Drive) is the exact type of storage that we're planning to use. It will act as a local disk. As per discussion with Support this morning he's not recommending me to use it since its not on the Compatibility List for it may or may not work. 

 Personally, I use eSATA, NOT USB for better performance.