It's not so much backcup exec working with iSCSI, it's you setting up your SAN to best maximize it.  When you get the best throughput from it, you'll get the best backup speeds via BackupExec.

Talk to the manufacturer for recommendations.  If Equallogic, they have great documentation, and the ADBO option works great.  They even have videos on the setup and config of it all.  If something else, good luck.

Well... it happens to be Equallogic + Symantec + Dell server + Dell powervault :)  the perfect business partners.

Thanks for the suggestion. I guess ADBO is the only way to go.

One more issue..... My total backup size exceeds the tape size and now spans over 3 tapes. BE2010 supports synthetic backup, can it help me in my scenario?

Please correct me if i am wrong.. .I am imagining this:

Sunday - Full 3 tapes backup

Mon - incremental #1

Tues - incremental #2

 and so on ..........

My target is Mon - Sat uses only 1 tape per day. Is it possible?

Synthetics ONLY work for file backcups.  It does not work with databases like exchange or sql, etc.

If you use synthetics, you'll have to backup to disk.  So you would be able to eliminate the tapes during the week and then take your synthetic full from disk adn duplicate it to tape.  There is a pre-built policy to help you with this when you are licensed for ADBO.  (ADBO includes snapshot backups and synthetic backups)

Tapes are cheap, it's the disk you should be worried about.  I've got some customers that have thousands of tapes under IBM Tivoli, and hundreds of tapes with NetBackup.  I recall a past client in LA (university) that used a StorageTek library the size of a minivan, that held thousands of tapes, and they had many more thousands offsite.

Use the latest Admin Guide and this link to read up on Synthetic backups

http://www.symantec.com/business/support/index?page=content&id=HOWTO21791

And pardon me for my lack of knowledge, does synthetic backup works on file level or block level?

This is because my exchange database .edb is the largest file and it will change n increase every day. If I use synthetic backup, will it get backup as well during the incremental synthetic backup? that file alone is 90% of the total backup, defeat the purpose of using synthetic if it is also treated as incremental backup.

Backup exec does a file level backup and synthetic backup is also a file level backup . IF you want to perform a block level backup I would suggest you to use backup exec system recovery 

synthetic backup works on file level and Do not include database backups in synthetic backups.  

Just to clarify as I am worried that a point is being missed here - the Exchange edb file will NOT be part of a synthetic backup as it counts as part of a database and should therefore be backed up via the Exchange agent (possibly with ADBO if you have supported off-host hardware)

Backup Exec can do Exchange incremental backups, which still use VSS, which might help with your issue.