We're looking to get a new SAN, and so we're re-examining our storage, network and backup issues. Our plan is to get an EMC VNXe 3100 with SAS drives for production data, then buy an expansion shelf and populate half of that with SATA (6 TB raw) drives. Our backup software will then use the SATA as the target.
Our initial sales rep said that would work fine, followed by another EMC sales rep (not coincidentally trying to sell a backup storage appliance, Data Domain) saying that you should never ever put the backup set on the same storage. I'm sure that would be better, but budget is a concern for us, and using the SATA seems a reasonable compromise, but I'd like to be sure.
In my mind, the disk backup target on SATA is to give us 1.) smaller backup window, and 2.) convenient tapeless recovery. We'll still be using tape for disaster recovery and using the backup software to move the disk backup to tape. We only have one site, so replication isn't a great option. Since budget is a concern for us, this seems reasonable as opposed to buying a special device.
The only failure mode I can think is if both controllers on the VNXe fail simultaneously, we're not going to be able to get to either production disk or disk backup. But the odds seem really low for that. Seems that if that happened, we'd be looking for the tapes anyway, because the server room would be gone.
So, am I crazy? Is there anyone else doing something similar?