An engineer wants the lowest-cost EBS volume for the root/boot volume of a new EC2 instance and is considering Cold HDD (sc1) to save money. What should they know before choosing it?
- sc1 is fully supported as a boot volume and is actually the recommended choice for minimizing boot volume cost
- sc1 can be used as a boot volume only if the instance is launched from an instance-store-backed AMI
- sc1 can be used as a boot volume only after Fast Snapshot Restore is enabled on the underlying snapshot
- sc1 (Cold HDD), like st1 (Throughput Optimized HDD), cannot be used as a boot volume at all; only SSD-backed volume types (gp2, gp3, io1, io2) support that role
Why D? And why not the others?
Correct answer: D. sc1 (Cold HDD), like st1 (Throughput Optimized HDD), cannot be used as a boot volume at all; only SSD-backed volume types (gp2, gp3, io1, io2) support that role
AWS's HDD-backed volume types, Throughput Optimized HDD (st1) and Cold HDD (sc1), are both explicitly documented as unsupported for use as a boot volume, because they're built for large, sequential throughput workloads like big data, log processing, and infrequently accessed storage rather than the small, random I/O a boot volume needs at startup; only the SSD-backed types, gp2, gp3, io1, and io2, are supported as boot volumes. The option claiming sc1 is fully supported, and even recommended, for boot volumes directly contradicts this restriction. The option conditioning boot-volume support on launching from an instance-store-backed AMI confuses two unrelated concepts: instance-store-backed AMIs don't use EBS root volumes at all, so an sc1 boot volume wouldn't apply to them either. The option suggesting Fast Snapshot Restore unlocks sc1 as a boot volume is wrong because FSR only removes the first-access latency penalty on a volume created from a snapshot; it has no effect on which volume types are eligible to serve as a boot volume.
Source: AWS EBS documentation: Amazon EBS volume types — boot volume support table (st1/sc1 excluded)