MongoDB on Amazon ec2 with SSD
The copy velocity and the full resync is amazing. Renaming fields went a lot faster, but not as much as we´d like.
Map-reduce of about 20 million documents took less than 10 minutes.
Renaming a field on 10 Million documents took 20 minutes. Renaming on 320 Million, however, took more than 19 hours....
Indexing is still a problem because mongodb uses only one core to do everything and can take as long as a common machine with attached EBS.
That said, in real life situations the %lock on the DB goes down to half of the normal and the background flush avg is less than 200 ms. I think that on the lung run it will be great once the paging starts to push the limits on our RAM.
Our app have never been faster, the paging are about 50/sec, but are almost unnoticed. We are expecting to reach 10 MM impressions this Sunday!
A few gotchas: we cannot save them as part of an AMI, so everytime you have to rebuild it, you have to make it with a full resync. And as of today Amazon only allows you to have two of those babies, so if you want more, you have to ask them...
Here´s how it compares in terms of %lock:
And here´s the SWEET IOP measures at the primary:
This weekend, I´ll put the newer iop provisioned EBS (http://aws.typepad.com/aws/2012/08/fast-forward-provisioned-iops-ebs.html) to work on a secondary, as the older ones are suffering at 50% lock and they could get into a state where they will not be able to catch up the primary.