幹壞事是進步最大的原動力
我在「把 blog 搬到 t4g.small 上」這邊有提到把這個 blog 搬到 Amazon EC2 的 t4g.small 上 (2GB RAM + 20% CPU credit)，跑了一陣子把 CPU usage 拉出來看：
當初估大約要 20% 的 CPU credit，結果發現 CPU credit 大概用 5% 就夠了。另外記憶體的部份大約要給 1GB，這個量可以看出來一些沒在用的 process 會被丟到 swap：
total used free shared buff/cache available Mem: 952Mi 380Mi 79Mi 110Mi 492Mi 368Mi Swap: 511Mi 152Mi 359Mi
把條件綜合起來計算，就往下降一階變成 t4g.micro 了 (1GB RAM + 10% CPU credit)。
另外新機種比較不用擔心淘汰速度，就看了一下 Reserved Instances 的價錢，一年 USD$44，三年 USD$84，看起來只要有用兩年就算是 OK，直接買三年解決掉...
Amazon EC2 的 Reserved Instances 宣佈降價：「EC2 Price Reduction – For EC2 Instance Saving Plans and Standard Reserved Instances」。
文章裡先列出 M5/C5/R5 的：
可以看到 R5 在一年是完全沒動，然後有些也是 0%，不過大多數應該是都有降：
Below I’ve given a snapshot of some of the savings across the M5, C5, and R5 instance types, however there are also price reductions for the instance types C5n, C5d, M5a, M5n, M5ad, M5dn, R5a, R5n, R5d, R5ad, R5dn, T3, T3a, Z1d, and A1.
以這些資料看起來是降了一些，但實際想要翻 T3a 系列機器的歷史資料時發現不好找，用搜尋引擎可以在「Where can I find Amazon EC2 price history?」這邊看到「https://pricing.us-east-1.amazonaws.com/offers/v1.0/aws/AmazonEC2/current/index.csv」這個地方，看起來是「New – AWS Price List API」這邊的資訊，不過看起來沒有 RI 的資料，只有 AmazonEC2 的資料 (所以對應到的都是 $0.00)。
之後看看有沒有其他地方有留這些資訊好了...
AWS 開始陸陸續續在推出有 100Gbps 能力的 EC2 instance 了：「New – EC2 P3dn GPU Instances with 100 Gbps Networking & Local NVMe Storage for Faster Machine Learning + P3 Price Reduction」。
從「Amazon EC2 Instance Types」這邊可以看到先前只有 c5n.18xlarge 有支援 100Gbps 網路，現在推出的 p3dn.24xlarge 是第二個支援的...
另外是 P3 系列的降價消息，比較奇怪的是從 2018/12/06 開始生效，而不是從月初開始。另外區域與條件也有一些複雜，有常在用的人可以翻一下說明...
Amazon EC2 推出了短期 RI 選項：「Amazon EC2 now offers On-Demand Capacity Reservations」。
最早的 RI 設計包括了「保證一定開的起來」與「折扣」，但後來 AWS 大概是發現大家都是要「折扣」而不是保證開的起來，所以就開放了只有 discount 的部份。把原來有保證一定開的起來的部份變成 Zonal Reserved Instances。
不過 Zonal Reserved Instances 最少要一年 (有對應的折扣)，這次規劃的 On-Demand Capacity Reservations 可以隨時取消，但是就沒折扣了：
Previously in order to achieve a capacity reservation, customers had to leverage Zonal Reserved Instances and commit to that capacity for a minimum of one year. Now with On-Demand Capacity Reservations, customers can reserve the exact capacity they need, in the location they need, and can keep it only for as long as they need it.
不過費用計算上會組合已經買的 Regional RI，如果沒被用掉的話還是可以將對應的折扣拿進來用：
If you have Regional RI discounts, they will automatically apply to any matching Capacity Reservation. This gives you the flexibility to selectively add capacity reservations and still get the Regional RI discounts for that usage.
算是對需要「保證開的起來」的單位提供短期的彈性，實際上後面應該是去 spot instance 那邊踢一些機器出來？XD
AWS 將本來 EC2 的 Spot Fleet 加上了 EC2 Fleet，計算的公式從本來只有 Spot Instace，變成把標準 EC2 Instance 與 RI 的計算全部都納進來：「EC2 Fleet – Manage Thousands of On-Demand and Spot Instances with One Request」。
Today we are extending and generalizing the set-it-and-forget-it model that we pioneered in Spot Fleet with EC2 Fleet, a new building block that gives you the ability to create fleets that are composed of a combination of EC2 On-Demand, Reserved, and Spot Instances with a single API call.
不過目前有些服務還沒整，主要是跟 auto scaling 有關的部份，這部份應該是一次上一大包：
We plan to connect EC2 Fleet and EC2 Auto Scaling groups. This will let you create a single fleet that mixed instance types and Spot, Reserved and On-Demand, while also taking advantage of EC2 Auto Scaling features such as health checks and lifecycle hooks. This integration will also bring EC2 Fleet functionality to services such as Amazon ECS, Amazon EKS, and AWS Batch that build on and make use of EC2 Auto Scaling for fleet management.
整完以後對於要省成本就更簡單了...
現在 AWS 讓你可以設定，是否允許 Reserved Instance (RI) 跨帳號使用：「Customize your organization’s AWS credit and Reserved Instance (RI) discount sharing using new billing preferences」。
以往是優先用在自己帳號，但如果有剩的話可以挪去其他帳號用。這樣雖然比較省錢，但有時候會造成帳務的「困擾」：
Historically, AWS has maximized customer savings by applying credits and RI discounts first to the account that owned the credit or RI lease and then distributing the remainder, if any, to qualifying usage incurred by accounts in the same organization. While this approach had the potential of lowering the overall bill, customers were unable to control if, and how, discounts were applied across organizational lines.
現在則是可以關掉：
To provide greater flexibility, customers can now disable AWS credit sharing across all accounts in their organization. This ensures that only the account that owns a credit, or has previously redeemed a credit, receives the associated benefit.
也可以分開設定：
You can also designate a set of accounts for which RI discount sharing is disabled, while continuing to share RI discounts among the rest of the accounts in your organization.
這樣雖然會比較貴，但這其實反應到某些組織文化上的問題啦...
Amazon EC2 的 CRI (Convertible Reserved Instance) 支援一年的合約了：「EC2 Convertible Reserved Instance Update – New 1-Year CRI, Merges & Splits」，這樣彈性再多了一些：
Today we are introducing Convertible RIs with a 1-year term, complementing the existing 3-year term.
不過 CRI 主要是用在需要換 family type 的情境下，如果是已知 family type (像是一般性的 worker 會選 C4 或是剛推出的 C5) 那麼就直接選擇 Regional RI 就好...
基本上就是讓財務操作上多個選擇 :o
AWS 宣佈 RDS 的 RI 也支援彈性計價了：「Amazon RDS Reserved Instances Offer Instance Size Flexibility」。
也就是說跟 EC2 的 RI 方式切齊，買 db.m4.2xlarge 的 RI 後，可以用在兩台 db.m4.xlarge 上：
For example, let’s say you purchased a db.m4.2xlarge MySQL RI in US East (N. Virginia). The discounted rate of this RI can automatically apply to 2 db.m4.xlarge MySQL instances without you needing to do anything.
包括了相當多種類的 RDS，主要是沒有 license fee 的類型都包括在內了：
Amazon RDS Reserved Instance size flexibility is offered in all regions for the MySQL, MariaDB, PostgreSQL, and Amazon Aurora database engines, as well as the “bring your own license” (BYOL) edition of the Oracle database engine. To learn more about flexible RIs, please visit the Amazon RDS Reserved Instances Page.
但不包括要另外收 license fee 的 SQL Server 與 Oracle LI edition：
Size flexibility does not apply to Microsoft SQL Server and the License Included (LI) edition of Oracle.
現在可以透過 AWS Budgets 來看到 Reserved Instance 的使用率了：「Monitor your Reserved Instance utilization by receiving alerts via AWS Budgets」。
Starting today, customers can now monitor and receive alerts when their Reserved Instance (“RI”) utilization falls below the threshold they define.
算是個開頭，不過我更想請 AWS 分析有哪些機器是長年開著沒有 discount 的... 或者像是 GCP 那樣自動算 :o
昨天 Amazon EC2 的 Reserved Instance 有了重大的變化：「EC2 Reserved Instance Update – Convertible RIs and Regional Benefit」。
當初 AWS 規劃 RI 的重點在於「保留」而不是「折扣」，所以在整體的規劃上你可以看到都是以「保留」為想法在規劃 (像是購買時要到 region + zone 的層級)。但其實更多人是看中他的「折扣」，所以 AWS 這次乾脆推出了不分區的「折扣」方案 (購買時只指定 region)，當然使用者就要規劃成 a 區開不起來就去開 b 區的機器：
Many customers have told us that the discount is more important than the capacity reservation, and that they would be willing to trade it for increased flexibility. Starting today, you can choose to waive the capacity reservation associated with Standard RI, run your instance in any AZ in the Region, and have your RI discount automatically applied.
另外是 RI 之間的轉換，現在可以透過系統直接轉不同 type 的 RI 了：
Convertible RIs give you even more flexibility and offer a significant discount (typically 45% compared to On-Demand). They allow you to change the instance family and other parameters associated with a Reserved Instance at any time. For example, you can convert C3 RIs to C4 RIs to take advantage of a newer instance type, or convert C4 RIs to M4 RIs if your application turns out to need more memory.
不過相較於隔壁的 Google Cloud Engine 的 discount 是完全自動算 (不需要先買 RI 這類的產品) 還是差了不少...