If you filled say a 8TB node on a regular CMR drive… then shut it down and moved it all-at-once to a 8TB SMR HDD… would you expect it to still perform OK (since it’s not still growing at 500-1000GB/month)?
Or would the small churn of trash->new-ingress still cause problems?
I feel it will work fine: amount of churn would correlated with current deletion rate, and people complain about how long it takes to reduce the node size – specifically because of the slow churn. So I’d say, it’s well within the capability of the smr disk to absorb.
However copying your data to that disk will take a while… I’d say, at least a week, if cloning the disk. Which means you can’t clone it – you’ll have to keep the node online, and take the multiple rsync approach. How many months will that take I won’t try to guess.
SMR usually does quite okay with sequential writes, therefore dd / cloning would be the more attractive option. Most of them have a sequential speed of 100-150MB/s, boiling down to less than 24 hours offline for a 8TB drive. That’s not so bad…