New Low End T2 Instances for Amazon EC2
Amazon have introduced T2, a new class of low cost general purpose instances for EC2 intended for workloads that don’t drive consistently high CPU usage. At the low end t2.micro offers higher performance, more memory (1GiB) and a lower cost (1.3¢/hr) than the previous t1.micro. The T2 class also offers small and medium sizing with 2GiB and 4GiB RAM respectively. T2 instances all offer burstable performance, which is intended for peaky workloads.
|Model||vCPU||CPU min/hr||RAM (GiB)||Cost ¢/hr|
The new CPU credits system offers a much more transparent approach to performance than the the previous generation t1.micro instances (which had their own detailed guide to performance considerations). Each size of instance comes with a number of CPU minutes available per hour, and these can be stockpiled over the course of a 24 hour period. When an instance gets busy it then draws down from the pool of available minutes. Additional performance credit is also offered to cover the boot up period, though any stockpiled credit is lost if a server is stopped and restarted. Amazon have introduced new CPUCreditUsage and CPUCreditBalance metrics to their CloudWatch monitoring systems so that users can keep track of their utilisation. Evangelist Jeff Barr has a worked example on the AWS Blog where he illustrates credit usage and credit balance whilst compiling a Linux kernel on a t2.small instance.
The T2 class makes use of Amazon’s Elastic Block Store (EBS), including the recently launched SSD-Backed variant. SSD volumes are twice the price (10¢/GB) of the older ‘magnetic’ volumes, but there is no longer any charge for I/O requests (which were previously 5¢ per million). Amazon have followed the Google model of tying performance to size with 3 sustained IOPS for every GB of storage. There are however two big differences between the Amazon and Google approach; Amazon’s performance guarantee falls in the logarithmic middle between Google’s standard and SSD persistent disks, and Amazon offers bursts up to 3,000 IOPS for each GB. The differing pricing structures make it increasingly hard to compare between suppliers, but Amazon have come up with something that whilst not offering ultimate performance is relatively inexpensive and flexible. At the same time as it launched SSD volumes Amazon also announced a 35% price cut for EBS volumes with provisioned IOPS, its offering for those demanding well defined performance guarantees.
Amazon show the T2 class as sitting on the ‘Intel Xeon family’ physical processor at 2.5 GHz without specifying a particular processor type (such as the E5-2670 that is used for pretty much every other current instance class except C3). This means that T2 instances can take advantage of newer Intel capabilities such as native instructions for AES encryption (AES-NI) Advanced Vector Extensions (AVX) for floating point and Turbo Boost where the CPU core can be made to run faster. T2 instances make use of a hardware virtual machine (HVM), and it’s recommended that HVM Amazon Machine Images (AMIs) are used in order to get best performance.
T2 instances are already available in all regions except US West 1 (Northern California), China and GovCloud. Availability in those remaining regions has been promised ‘in the near future’.
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