17 months ago I blogged about 900TB (nearly 1PB) in 1U of rack space for only $60k. There I noted that a 1U server for the new high-density SSDs wasn't commonly available. Well, that has changed. A couple of months ago, Super Micro announced their 32-bay 1U unit for 2.5" drives. With the 32TB SSDs that Samsung announced last year to be available this year, that yields 1PB.
It won't be cheap. Recall that the 900TB 4U for $60k was for spinning drives. Given that the 16TB SSDs go for nearly $12k a pop, the 32TB drive that has been slated for later this year would be at least twice that and likely much more initially. Even at $24k for each 32TB SSD, this 1U of 1PB SSD would set you back $800k.