Official update for EBS performance
EBS RANDOM READS:
100 IOPS for small (8K) random read.
8MB/s for larger (64K) random reads.
Service time is around 5-10 ms best case, but can be 100 ms under heavy load.
EBS RANDOM WRITES:
200 IOPS for small (8K) random writes due to deep caching EBS.
Burst write tend to be much better than burst reads.
EBS STREAMING I/O:
EBS optimized for random I/O, not sequential streaming EBS streaming.
Sequential reads will be network-limited to about 80 MB/sec.
Note that striping multiple EBS volumes will *not* help this (Striping ephemeral drives *will* help streaming performance).
Striping (RAID 0) can be used to increase EBS random read / write IOPS.
Generally does not make sense to use higher RAID levels, since EBS volume is already mirrored (EBS RAID 0 is functionally equivalent to a stripe of mirrors).
Performance tends to be reasonably linear (more EBS volumes gives more random IOPS) up to about 8 devices. If more than 1000 IOPS are needed, consider using an in-memory cache (Amazon ElastiCache) to provide the effect of higher IOPS.
These statistics are from Amazon Sales Development Representative, Kesavan Nair.
Many thanks here!