I dissagree with you on the RAID 0 issue if the following is true. There is a duplicate job from the disk to tape. with modern server hardware prefailure detection (assuming you are using an actual server not a white box or pc) RAID0 should not be an issue, also te intent of the symantec support is to eliminate a disk write bottleneck. RAID5, 4, 6 ADG should never be used in a B2D environment due to the excessive write overhead. RAIDs 0,1,10,0+1 depending on you vendor will reduce or eliminate (in the case of RAID0) any write penalty. Once again raid 0 only if you are dumping to tape immediately after the B2D. comments about B2D being slower are in fact not entirely true. in an exchange backup scenario, you are limited based on disk file fragmentation, number of spindles, raid level, network config and Server load. in fact i have found that B2D will shave almost 10-20 percent off a comperable B2Tape time of the same data (I have logs to prove it).
My Exchange Backup Best Practices:
1) Limit your mail stores to 1-2 per raid set Mirror drives reccomended Hot Spare Optional (notice i did not say drive)
2) max out your memory in the server (4GB for 32bit and as much as you can afford or server can handle on 64bit)
3) Use real server hardware. no High performance pc's, ata/sata drives, software raid.
4) Use high quality network switches (Cisco, HP, nortel, extreme...) that support LACP for multiple NIC's to provide high Bandwidth.
5) Set all NIC's and Switchports manually Gig/Full and test throughput.
6) Make sure ALL your drivers and updates are applied to your servers, Os, network cards, and your switch firmware is also up to date.
7) also check all your SCSI settings or SAS settings. if you are using USB for your tape drive or to an external disk, Trade up.
Example B2D config:
Exchange server:
HP DL380 g5 2x QC 2.13 proc, 16GB ram, 8 15k 146GB drives (4 - R1+0) SAS, windows 2008 x64
Backup server:
HP DL380 g4 2 x DC 1.8 proc, 4GB ram, 2 x 15k 72GB drives (Boot), 14 x 146g 15k RAID0) + HP MSL4048 LTO3 SCSI.
job dumps to disk and then duplicates immediately to tape.
500g B2D 19 hours from exchange, 500G File backup 4.2hr.