Do Amazon High I/O instance guarantee disk persistence?

Question

The High I/O instance in EC2 uses SSD. How does one run a database on such an instance while guaranteeing persistance of data?

From my limited understanding, I'm suppose to use Elastic Block Store (EBS) so that even if the machine goes down the data on the disk doesn't disappear. On the other hand the instance storage SSD of a High I/O instance is ephemeral and can't be used for database storage because if, for example, the machine loses power the data image isn't preserved. Is my understanding correct?

Answer 1

Point 1) If your workloads need High IO SSD for DB, then you should have Master Slave setup. Ideally 1 master and 2 slaves spread across 3 AZ's is suggested. Even if there is an outage on single AZ the alternate AZ's can handle the load and serve your High availability needs. Between master - slave you can employ synchronous, semi or async replication depending upon your DB. This solution is costlier.

Point 2) Generally if your DB is OLTP in nature, then Amazon EBS PIOPS + EBS optimized gives you consistent IOPS. A Single EBS Volume can provide 4000 IOPS and you can RAID 0 multiple volumes and gain 10k+ IOPS for performance. Lots of customers are taking this route in AWS. Even though you may use EBS for persistence, it is still recommended to go with Master-Slave architecture for High Availability. I have written detailed articles on this topic in blog, refer them for more information.

Answer 2

It is the same as other ephemeral storage, it does not guarantee persistence. Persistance is handled by replication between instances with at least one instance writing to an EBS volume.

Answer 3

If you want your data to persist, you're going to need to use EBS. Building a database on an ephemeral drive, regardless of performance, seems a dubious design choice.

EBS now offers 4K IOPS volumes, which is, depending on your database requirements, quite possibly more than sufficient.

My next question would really be: Do you want to host/run your own database?

Turnkey products such as RDS and DynamoDB may be sufficient for your needs. Using them is much easier than setting up and managing your own database. RDS is now advertising "You can now provision up to 3TB and 30,000 IOPS per DB Instance". That's enough database horsepower for many, many problem sets.