DNS (GTM) best practice for DR

After some test my idea for scenario when each Slave has separate FQDN and IP is:

• Create as many Wide IPs as Slave FQDN
• Wide IP Load Balancing Method: Global Availability
• Create pair of Pools for each WideIP:
  • PoolDC1-1 to 8 for Slaves in DC1
  • PoolDR1-1 to 8 for Slaves in DR1
  • In each pool pair first Member is the one that should be returned when DNS query for given Wide IP is performed, only if it's down next member IP is returned, and so on until there is no active member left (whole pool down)
• LB at Pool level set to:
  • Preferred: Global Availability
  • Alternate: Round Robin (probably could be None, or maybe should?)
  • Fallback: None (this is a must)
• Assign appropriate pool pairs to each Wide IP, Member Order:
  • PoolDC1-1 to 8
  • PoolDR1-1 to 8

Result are: If for given Wide IP member that is default for FQDN is down - like slave1.vip.site.com should return 192.168.1.1, slave2.vip.site.com - 192.168.1.2 etc. - then next IP is returned (for example 192.168.1.3) If all member of pools PoolDC1-1 to 8 are down then members from pools PoolDR1-1 to 8 are returned.

Is that make sense? Any better/easier/more robust config could be used?

Last question is (for scenario with one FQDN for all Slaves - BIG-IP DNS makes LB decision) how to configure when we have only one host performing queries (Main) and it needs persistence.

I know that it can be set at Wide IP level but how it works - similar to src addr affinity? So if request is from the same IP then for period set in Persistence TTL same IP will be returned.

Is this Persistence TTL refreshed after each request from same IP?

If there is no request during set value then next request from same IP will be LB according to method set.

LB Method related to Persistence is the one set at Wide IP or Pool level?

Piotr