VM snapshot backup with backup LAN
The reason Marianne suggested using SAN is because, the backup data would move like this:
LUN -> SAN -> Media server -> STU
...with this model the media server reads the LUNs directly, and ESXi has to do very little IO work for backups.
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...however, if you use LAN - then the data has to move "through" a server that can see the VMFS storage, and this will most probably mean data will be moved via an ESXi host, .e.g:
LUN -> SAN -> ESXi host -> LAN -> Media server -> STU
...i.e. the NICs, CPUs and RAM of the ESXi host do the bulk of data moving. And if you have puny/small (not very good) LAN switches that are not fully segregated (in IO bandwidth terms) from the normal network traffic - then the LAN networking could struggle.
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IMO - circa 100 VM's is a fair sized environment, and could probably warrant SAN LUN sharing to NetBackup. But, probably best to see how you get on first - because a "bottleneck" might never reveal itself to you, in which case everything will always appear to be fine, and when infrastructure appears to be fine, then it usually is fine. N.B: There is always one or more bottleneck(s) in any and all environments - however, you may never notice where it is, or where they are, unless you start having 'IO' issues or start failing to meet SLAs or start hearing complaints about slowness etc.
SAN vs LAN - it's all discussion points :)
Back to your questions:
SAN transport will only be used if NetBackup has a path. No FC cabcling, no SAN zoning, no LUN presentation = no SAN backups.
Yes, for NFS use nbd mode.
Yes, sounds like a good idea to use a backup LAN for all backup traffic - things are usual easier to manage if everything used in 'backup land' has '-bck' on the name, then you know it's trying to use those names and IPs and so should be using backup VLANs... whether it actually is or not will be down to the network configuration of gateways and routing.
Yes, if you want NBD transport backup traffic to travel over physical NICs reserved for backups on the ESX hosts then you can use DNS names with '-bck' and IPs to the ESXi hosts using the backup VLANs. Shouldn't be a problem. Yes, you shoud be abelt to get eveything to use backup VLAN. It shouldn't bee too difficult.
