I have managed to successfully download the blast nt database as a volume on my ec2 instance by running the following command on my mounted volume:
cd /mnt/blast_mount
update_blastdb --decompress nt
Running blast against nt after works just fine and takes about 20 minutes.
I added the volume to /etc/fstab so that it will automatically mount in future instances, and then saved my instance including the volume as an ami. When I launch an instance from the ami, I see the mounted volume is there with all the blast nt files. However running blast using the db hangs indefinitely. I see in htop that it is running but its been many hours for one short sequence and still isn't done.
The newly launched instance has the same parameters as the original instance that worked (instance type, security groups, subnet...).
If I erase the entire nt database and redownload it then blast works fine again.
I also tried download the blast db directly to my instance without adding an ebs, and saving the instance as an ami. Here too, the instances launched from the ami seem to have all the nt files but blastn hangs indefinitely.
What could be wrong here? I did the same process saving the interpro db on a different volume and made an ami and it works just fine