Q: What factors should be considered with regard to a customer's backup method?
If you are using a SAN array and want to do serverless backup, this will imply that snapshots are involved and that a different host will be required to have access to the snapshot of that LUN. This has storage implications and also management implications in terms of switch zoning, LUN masking and software costs.
If you are using a NAS array, you may want to consider using NDMP. There will be infrastructure considerations (such as backup HBAs and SAN ports if backing up over a tape SAN), and in most cases licensing implications with your backup application when using this method. However, this is typically a best practice for most midsize to large NAS arrays.
If VMware is involved, you will want to consider doing backups at the ESX Server level or using VMware Consolidated Backups (VCBs). If snapshots are used in conjunction with these, the amount of storage required needs to be considered.