Okay.
Hello cloud gurus and welcome to this lecture and this lecture we're going to talk about.
Easy to placement groups so congratulations you're almost at the end of the E2 section of the course
you've done really really well.
Hopefully you've learnt an awful lot and had an awful lot of fun in this one it's just a pure theoretical
lecture easy to placement groups do come up on the exam they used to be only one type of placement group
and they used to be very popular exam topic now there's three different types of placement groups and
you will need to understand what they are going into your exam and the differences between the three.
So what does a placement group are an easy to placement group.
Well it's pretty obvious from the name actually it's just a way of placing your easy two instances and
there's three different types of placement groups.
So we have our clustered placement groups our spread placement groups and then our partitioned placement
groups and we'll go through each one individually it will start off with the easiest so clustered placement
groups is basically a grouping of instances within a single availability zone placement groups are recommended
for applications that need low network latency high network throughput or both.
So essentially it's a way of putting your easy to instances very very close to each other so that you
have very low network latency and you can also have very very high network throughput so that's all
it is it's a way of grouping your easy to instances very very close together within a single availability
zone and only certain instances can be launched into a clustered placement group.
We then have our spread placement group and this is basically the opposite idea.
So it's a group of instances that are each placed on distinct underlying hardware so these will be on
separate racks with separate network inputs as well as a separate power requirements.
So if you have one rack that fails it's only going to affect that one easy to instance.
So spread placement groups are recommended for applications that have small number of critical instances
that should be kept separate from each other and you can have spread placement groups inside different
Availability Zones within one region and with a spread placement group.
I want you to think of individual instances so this individual easy to instance is on this individual
piece of hardware and it's completely isolated from this individual easy to instance this one et cetera.
So if a rack does go through and fail it's only going to affect the one instance.
So that's all a spread placement group is it's the sort of opposite of a clustered placement group in
that you know cluster placement group puts all your easy to instances very very close together so you
get really high performing network throughput as well as low latency risk spread placement groups are
designed to protect your easy two instances from hardware failure but it's individual instances put
on individual racks inside either the same availability zone or different Availability Zones depending
on how you can figure it out.
We then have partition placement groups which are very very similar to spread placement groups except
you can have multiple AC two instances within a partition.
So in using partition placement groups Amazon AC two divides each group into logical segments called
partitions and Amazon easy to ensures that each partition within a placement group is on its own set
of racks and Each rack has its own network and power source and no two partitions within the placement
group shared the same racks allowing you to isolate the impact of hardware failure within your application.
So if you go through and read the documentation it does take a little while to get your head around
the difference between a spread placement group and a partition placement group and basically the difference
is as you can have multiple instances in a partitioned placement group.
So you can have multiple instances on this rack and you can have multiple instances on this rack and
this rack is completely separate to this racks.
Easy two instances are basically setting on partition one and then you've got a whole bunch of easy
two instances sitting on partition two that's a partition placement group but if you're dealing with
individual easy two instances then that's a spread placement group.
So spread placement group is for single instance partition placement groups are for multiple instances
and then you're clustered placement groups are just a way of putting everything as close together as
possible.
So onto my exam tips just remember the three different types of placement groups so we've got our clustered
placement groups our spread placement groups and our partition placement groups.
So what is the use case for a clustered placement group.
What's for low network latency and high network throughput.
So you want your easy two instances to be as close to each other as possible they'll always be in the
same availability zone in the same region our spread placement group is where we've got individual critical
easy two instances and we need them to be on separate pieces of hardware.
So if one piece of hardware fails it's going to isolate that easy to instance it's not going to knock
out too easy two instances at once it's only going to be that one easy to instance it's all a spread
placement group is and then partitioned is for multiple E2 instances since it's use cases for this could
be reached DFS each base and Cassandra clusters so partitioned is basically just multiple easy two instances
whereas spread is individual critical easy two instances a cluster placement group can't span multiple
Availability Zones whereas a spread placement and partition to placement group can.
But they still have to be within the same region the name that you specify for a placement group must
be unique within your E.W. s account only certain types of instances can be launched in placement groups.
So these are things like compute optimize GP you memory optimized and storage optimized as well a W
S recommend homogenous instances within clustered placement groups if you are doing a clustered placement
group you want to have the same easy to instance types inside that cluster placement group or at least
that's Amazon's recommendation.
You can't merge placement groups and you can't move an existing instance into a placement group.
What you can do is create an AMA from your existing instance and then launch that instance from the
AMA into a placement group.
So that is it for this lecture everyone if you have any questions please let me know.
Congratulations for getting it to the very end of the E2 section of the course and the next lecture
we're just going to summarize everything that we've learnt in this section of the course and then we'll
be able to move onto the next section so if you've got the time please join me in the next lecture.
Thank you.