I wont deploy WAN Accelerator anymore , since your got a good bandwitch and for sure you got low latency. For me WAN Accelerator only add complexity to the backup, and another item to mantain.

I assume that your going modify your SORB and add a second copy (“on-fly”)  to the DataDomain with Retention Lock Enabled…

In this case , Veeam server should have conectivity with the Datadomain to manage conection. VPN / MPLS or Dark Fiber over your DC’s.

Hey,
 

May I know:

• WAN Accelerator required on both sites? how much resource in vCPU/vRAM and disk required?
  Yes WAN accelerators work in pairs: one WAN accelerator is deployed at the source site and another at the target site. 
  In you case as mentionned by ​@edh is maybe not necessary. 
• Gateway server should be deployed on production or DR site? how much resource needed?
  Which type of connection will be used between the gateway and the DD Fiber Channel ?
• Can use BCJ from Linux repo to DataDomain?
  Yes
• This will not affect enable of RetnetionLock feature?
  Veeam Backup & Replication supports only the compliance mode of Dell Data Domain retention lock. Dell Data Domain with enabled immutability works similarly to the hardened repository

The connection interface of DD is 25G Ethernet SFP28

The WAN link is 10Gbps

if I place gateway on production site, veeam proxies are there, but the DD on DR site will not work if primary site down…

if I place gateway on DR site, since the dedupe will happen on the gateway, the un-dedupe data travel along the WAN, which is not good for network utilisation

or should I have 2 gateway server, placing one on each site?

or could I have active/standby gateway?

Your DR will not work without the Veeam Backup Server up.

I suposee that Veeam Backup server is on primary site , correct?

Your just getting a Off-Copy managed by a Veeam Server. For access your data in case of event, you will need to restore the Veeam Server on secondary site, enable the proxy needed or re-add and re-scan the DD.