{"id":1629,"date":"2016-09-12T13:01:28","date_gmt":"2016-09-12T12:01:28","guid":{"rendered":"http:\/\/www.tekhead.org\/blog\/?p=1629"},"modified":"2016-10-11T11:01:31","modified_gmt":"2016-10-11T10:01:31","slug":"amazon-aws-tips-and-gotchas-part-8-reserved-instances","status":"publish","type":"post","link":"http:\/\/tekhead.it\/blog\/2016\/09\/amazon-aws-tips-and-gotchas-part-8-reserved-instances\/","title":{"rendered":"Amazon AWS Tips and Gotchas \u2013 Part 8 \u2013 AWS EC2 Reserved Instances"},"content":{"rendered":"

Continuing in this series of blog posts taking a bit of a \u201cwarts and all\u201d view of a few Amazon AWS features, below are a handful more tips and gotchas when designing and implementing solutions on Amazon AWS, including AWS EC2 Reserved Instances.<\/p>\n

For the first post in this series with a bit of background on where it all originated from, see here:
\nAmazon #AWS Tips and Gotchas \u2013 Part 1<\/a><\/p>\n

For more posts in this series, see here:
\nIndex of AWS Tips and Gotchas<\/a><\/p>\n

AWS Tips and Gotchas \u2013 Part 8<\/b><\/span><\/h4>\n

Reserved Instances<\/a> are a great way to save yourself some money for instances you know you will require for a significant period of time (from 12-36 months). One really cool fact which AWS don’t announce enough, in my opinion, is that reserved instances can actually be shared across consolidated billing accounts<\/a>!<\/p>\n

If you wanted to, you could purchase all of your reserved instances from your primary consolidated billing accounts, however, it doing this has some potentially unexpected results:<\/p>\n

    \n
  1. Reserved instances don’t just provide you with a better price, they also provide you with guaranteed ability to spin up an instance of your chosen type, regardless of how busy the AZ in question actually is.
    \nIf there is an AZ outage, other AWS customers will scramble to spin up additional instances in other AZs in the same region, either manually or via ASGs, and this has the potential to\u00a0starve the compute resources for one or more instance types!
    \nYes, that’s right,\u00a0    even AWS do not have an infinite compute resources<\/a>!\"AWS<\/a>By using reserved instances, you are still guaranteed to be able to run yours regardless of available capacity for on-demand instances. They are truly reserved.
    \nIf however, you centralise your reserved instances into your CB account, you will get the reservation pricing benefits at the top of the account tree, but you don\u2019t get the capacity reservations as these are account specific.<\/li>\n
  2. Reserved instances are specific to individual Availability Zones<\/a>, so ensure you spread these evenly across your AZs\u00a0to avoid wasting them (you are of course designing your apps to be resilient across AZs, right?)\u00a0and give you maximum reserved coverage in the unlikely event of a full AZ outage.<\/li>\n
  3. And finally… Reserved instances are a commercial tool applied after-the-fact, not against a specific instance. When using consolidated billing\u00a0for reserved instances, the reservations\u00a0are therefore effectively split evenly across all accounts. If you actually want to report back to each business unit \/ account owner on their billing including reserved instance, this could be tricky.<\/li>\n<\/ol>\n

    Find\u00a0more posts in this series here:
    \n    Index of AWS Tips and Gotchas<\/a><\/p>\n

    Amazon AWS Tips and Gotchas – Part 9 – Scale-Up Patching<\/a><\/p><\/blockquote>\n