Setting a backup server

[Granty1]

Hi
I have just added a block account to back up my main account, Main is Supernews Backup is tweaknews, I wasn't sure how big the block needed to be so I started on the very small 10gb as I only intend to use it for the missing file parts.
I have searched a few threads and can't seem to workout how to set Tweak as a backup unless that simply setting priority to a number other than zero (Supernews default) and between 1 & 100 forces that to only be used as a backup?
The way I understand it is that there is a main pool, a backup pool and an optional setting.
I think sab will use either of my servers the way they are currently set, if both are set as a main and eat up my 10gb limit on tweak in no time unless I can change it to backup right? both servers are working but clicking on them I see no backup check box, I have seen a screenshot showing a backup option within these forums but I cannot seem to find it on the servers tab within sabs interface?
Any help greatly appreciated, thank you!

[shypike]

Quote from the Wiki.

SABnzbd 1.0.0+ uses server priorities instead.
This means that SABnzbd will first ask the highest priority server (0) and when that
server doesn't have an article, the next lower priority server (1) will be asked.
This continues until all (enabled) servers have been tried.
Servers within the same priority group will be used in a round-robin way (faster servers will be used more).

[Granty1]

Thanks Shypike

The info I came across must have been outdated.