As previous post I’m in the last few days of moving about 60 #websites to a new server. Today was meant to be the last day, moving the main domain over. It went utterly tits up.
Set up the main domain and its subs on the new server, move all files over, then updated the DNS. 10mins later the server hit max load with swap file at 99.8%!
Hours trying to work out the issue found nothing, eventually reverted all DNS. Tomorrow I’ll start changing DNS entries one at a time.
@Steveb Sounds stressful 
@mikehindleuk it’s a frigging nightmare. The error logs just kept pointing to mail boxes going into overload, but there was nothing new or wrong with them.
I’m now convinced either a DNS setting updated badly (is that even a thing?) or one of the many DNS entries is creating some sort of loop.
@Steveb Yikes! Hate stuff like that. Not sure if that's a thing, to be honest. I'm not overly technical in that department 
Hope you manage to get it sorted tomorrow...
@Steveb tough one that. Hope it all works out tomorrow
@Steveb hope you remembered to set a short TTL on the new record 
@Padjo 900secs. Would you suggest shorter?
@Steveb I’d usually drop to max 300 for something like this, but 900 isn’t too bad. In my youth I messed up a DNS record with an 86400 TTL. It’s an experience I never want to repeat! Hard to explain to a client that their site won’t fully recover for a day!
@Padjo lol.
In truth, I don’t much understand a lot of this stuff. I just make it up as I go along and hope.