I am trying to wrap my head around EC2 instances, and I am having a bit of an issue. I heard from a friend of mine that Amazon will kill EC2 instances, and then they restart the image (thus losing all state). Unless it uses EBS as a backing store, you get no persistence.
But I have been looking into Xen and it seems like instances should easily migrate instead of being killed/restarted.
So, do Amazon EC2 instances randomly stop/start an image with all state being managed by something external like EBS?
Amazon EC2 instances will not be stopped/started/restarted unless you issue a command to do so.
In some situations (eg hardware maintenance), you might receive a request from Amazon asking you to stop & start your instance (which moves it to a different host). Such requests are typically issued with two weeks notice.
One AWS customer told me that their instance had been running continuously for over three years.
Yes it is quite possible that an EC2 instance dies and is replaced. Depending upon your data, you may need to use EBS, EFS or S3 to prevent data loss in such cases.
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So I am noob, and just started learning about cloud computing and how AWS works.
Aws provide us the EC2 as service, Where I can run VM and put my data on top of it or say run my web server on top of the newly created instance.
I have seen people creating multiple instances in the same AZ.
Doesn't that leads to Redudant data, I mean we are creating more EC2 instances in the same AZ and putting the same data on each insances, so that when one gets called off, the client can access the data from another instance.
My question is this the industry practice to keep the redudant data (same data) across all the instances for better reachability or we are not putting the whole data on other instances just a fraction of it.
Please don't mind my stupid question, I am just learning.
Usually, when you run several instances of the same application, you run them in autoscaling group (ASG). For this, your applications should be stateless, as instances in ASG can be launched and terminated at any time automatically. To protect from data lose and ensure that new instances have access to existing data files, you don't store any user-data (e.g. user uploaded images) on the instances.
Instead you are going to store the data files outside of your instances. Common choices for that are S3 and EFS. This solves the data redundancy issue, as you only have one copy of your files which can be accessed from all the instances. Also it protects your data from being lost if your instances will get terminated, as S3 and EFS are highly-available and fault resistant data stores managed by AWS.
We have an EC2 instance running in AWS EC2 instance. We have our ML algorithms and data that. We have also hosted a web-based interface also in that machine.
Now there are no new developments happening in that EC2 instance. We would like to terminate AWS subscription for a short period of time (for the purpose of cost-reduction and exploring new cloud services). Most importantly, we want to be in a position where we can purchase a new EC2 instance with a fresh AWS subscription, use the backup which we take now, and resume all operations (web-backend, SMS services for our app which is hosted in AWS, etc.).
What is the best way to do it? Is temporary termination of AWS subscription advisable?
There is no concept of an "AWS Subscription". AWS is charged on-demand, which means you only pay when you use resources.
If you temporarily do not want the Amazon EC2 instance, you could:
Stop the instance, which is like turning off the power. You will not be charged for the instance, but you will still pay for the disk storage attached to the instance. You can simply Start the instance again when you wish to use it. You will only be charged while the instance is running. OR
Create an image of the instance, then terminate the instance. This will create an Amazon Machine Image (AMI), which contains a copy of the disks. You can then launch a new Amazon EC2 instance from the AMI when you wish to use it again. This is a lower-cost option compared to simply stopping the instance, but it takes more effort to stop/start.
It is quite common for companies to stop Amazon EC2 instances at night or over the weekend to reduce costs while they are not needed.
EDIT: Just thought of a third option. Will test it and be back. Not worth it; it would involve creating an image from the EC2 instance and then convert that image to a VM image, storing the VM image in S3. There may be some advantages to this, but I do not see them.
I think you have two options, both of them very reasonably priced. If you can separate the data from the operating system, then your best option would be to use an S3 bucket as a file system within the EC2 instance. Your EC2 instance would use this bucket to store all your "ML algorithms and data" and, possibly, even your "web-based interface". Whenever you decide that you no longer need the processing capacity of the EC2, you would unmount the S3 bucket file system from the EC2 instance and terminate that instance. After configuring an appropriate lifecycle rule for the S3 bucket, it would transition to Glacier, or even Glacier Deep Archive [you must considerer the different options of long term storage]. In the future, whenever you want to work with your data again, you would move your data from Glacier back to S3, create a new EC2 instance, install your applications, mount your S3 bucket as a file system and you would have access to all your data. I think this is your least expensive and shortest recovery time objective option. To implement this option, look at my answer to this question; everything you need to use an S3 bucket as a regular folder inside the EC2 instance is there.
The second option provides an integrated solution, meaning the operating system and the data stay together, and allows you to restore everything as it was the day you stopped processing your data. It's made up of the following cycle:
Shutdown your EC2 and make a note of all the specs [you need them further down].
Export your instance to a virtual image, vmdk for example, and store it in your S3 bucket. Something like this:
aws ec2 create-instance-export-task --instance-id i-0d54b0682aa3998a0
--target-environment vmware --export-to-s3-task DiskImageFormat=VMDK,ContainerFormat=ova,S3Bucket=sm-vm-backup,S3Prefix=vms
Configure an appropriate lifecycle rule for the S3 bucket so that it transitions to Glacier, or even Glacier Deep Archive.
Terminate the EC2 instance.
In the future you will need to implement the inverse, so you will need to restore the archived S3 Object [make sure you you can live with the time needed by AWS to do this]
Import the virtual image as an EC2 AMI, something like this [this is not complete - you will need some more options that you saved above]:
aws ec2 import-image --disk-containers
Format=ova,UserBucket="{S3Bucket=sm-vm-backup,S3Key=vmsexport-i-0a1c382e740f8b0ee.ova}"
Create an EC2 instance based on the image and you're back in business.
Obviously you should do some trial runs and even automate the entire process if it's something that will be done frequently. I have a feeling, based on what you said, that the first option is a better option, provided you can easily install whatever applications they use.
I'm assuming that you launched an EC2 instance from a base Amazon Machine Image and then added your own software and models to it. As opposed to launched an EC2 instance from an AWS Marketplace offering.
The simplest thing to do is to create an Amazon Machine Image (AMI) from your running EC2 instance. That will capture the current state of the instance and persist it in your AWS account. Then you can terminate the instance. Later, when you want to recreate it, launch a new instance, selecting the saved AMI instead of a standard AMI.
An alternative is to avoid the need to capture machine state at all, by using standard DevOps practices to revision-control everything you need to recreate the state of a running machine.
Note that there are costs associated with an AMI, though they are minimal ($0.05 per GB-month of data stored, for example).
I had contacted AWS customer care regarding this issue. Given below is the response I received. Please add your comments on which option might be good for me.
Note: I acknowledge the AWS customer care team for their help.
I understand that you require some information on cost saving for your
Instance since you will not be utilizing the service for a while.
To assist you with this I would recommend checking out the Instance
Stop/Start link here:
==>https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Stop_Start.html .
When you stop an Instance, you do not lose any data & you are not
charged for the resources any further. However please keep in mind
that you will still be charged for any EBS Storage Volumes attached to
the stopped Instance(s).
I also recommend checking out the below links on how you can reduce
your costs.
==>https://aws.amazon.com/premiumsupport/knowledge-center/reduce-aws-bill/
==>https://aws.amazon.com/blogs/compute/10-things-you-can-do-today-to-reduce-aws-costs/
That being said, please note that as I am in the billing department,
for the best assistance with the various plans you will require the
assistance of our Sales Team.
The Sales Team will be able to assist with ways to save while
maintaining your configurations.
You will be able to reach the Sales Team here:
==>https://aws.amazon.com/websites/contact-us/.
Once you have completed the details in the link, a member of the team
will be in touch with you at their soonest.
Our current server consisting of an 2x EC2 instances and RDS (Read/Write) database is in Mumbai Region. However I would like to copy everything (2x EC2 & RDS (R/W)) across to Sydney, and other to other regions.
Ideally I would like to replicate the contents in those instances as well.
Does anyone know a quick and easy way of doing this?
Edit 25/01/2019:
However I would like to copy everything including what ever is inside the instances (2x EC2s and the RDSs)
Edit 29/01/2019:
The purpose is to "scale/expand out". I want to have the same infrastructure replicated 1-to-1 (exactly/identically) across various regions.
It is simple!
- For EC2 - you need to create an AMI of those instances then right click on the AMI you've just created and choose "copy AMI" to the designated region.
For RDS
If you just wanna copy data to another region then take a snapshot then copy that snapshot to destination region
If you want to make the RDS replicate to another region continuously then you need to create a read-replica from your RDS instance.
Option for replicating environment depends on how much downtime can you tolerate.
If you are okay with downtime
1. Copy the AMI of EC2 instance and snapshot of RDS to another regions
2. Bring up your new environment.
This is perfect for non critial workload
If this is critical application
1. Copy the AMI of ec2 instance ( I am assuming this would be your web/app instnaces) For real time replication use rsync or robocopy .. or solution like cloudendure .
2. Create a new RDS instance in sydney
3. USE DMS migration tool .. create source and target relationship
4. once insync cut off the relation bring new environment in sydney
As suggested by previous answers for EC2 you can create AMIs and then move the AMI to a different region.
For RDS, you can either create read replicas (and read replicas of read replicas, but beware of latency), read replicas are used to mainly improve read performance of your app.
You can also create a Multi AZ backup which will act as a disaster recovery site. However, note that Multi-AZ is only used in case of a failover. Moreover, Multi-AZ involves Synchronous data copy and read replicas are asynchronous, so read replicas can demonstrate eventual consistency behavior.
But the real question here is - What are you trying to achieve?
Are you trying to "scale out" your infrastructure to support huge traffic to your application? Or are you simply trying to setup disaster recovery (DR)?
If your answer is DR, then the approach is pretty straight forward with Multi AZ and EC2 instance snapshots. But if the answer is scaling out and performance, you really need to be thinking of better strategies such as using Cloudfront (CDN) if it is a web app, using Elasticache in-memory cache for frequently read data, or RDS read replicas, using Elastic Load Balancers with Dynamic/Step scale-out/scale-in. Other, methods would be to evaluate the type of RDS storage subsystem used i.e. using Provisional IOPs vs. Using General Purpose SSD, checking if there are any NAT “instance” bottlenecks in your VPC and so on.
It may be tempting to spin up all these redundant copies of EC2 AMIs or RDS read replicas with a click of a button, but you really need to be thinking about the cost you are going to incur on a monthly basis for completely un-used resources.
Anyone have a sound strategy for implementing NFS on AWS in such a way that it's not a SPoF (single point of failure), or at the very least, be able to recover quickly if an instance crashes?
I've read this SO post, relating to the ability to share files with multiple EC2 instances, but it doesn't answer the question of how to ensure HA with NFS on AWS, just that NFS can be used.
A lot of online assets are saying that AWS EFS is available, but it is still in preview mode and only available in the Oregon region, our primary VPC is located in N. Cali., so can't use this option.
Other online assets are saying that GlusterFS is a way to go, but after some research I just don't feel comfortable implementing this solution due to race conditions and performance concerns.
Another options is SoftNAS but I want to avoid bringing in an unknown AMI into a tightly controlled, homogeneous environment.
Which leaves NFS. NFS is what we use in our dev environment and works fine, but it's dev, so if it crashes we go get a couple beers while systems fixes the problem, but on production, this is obviously a no go.
The best solution I can come up with at this point is to create an EBS and two EC2 instances. Both instances will be updated as normal (via puppet) to maintain stack alignment (kernel, nfs libs etc), but only one instance will mount the EBS. We set up a monitor on the active NFS instance, and if it goes down, we are notified and we manually detach and attach to the backup EC2 instance. I'm thinking we also create a network interface that can also be de/re-attached so we only need to maintain a single IP in DNS.
Although I suppose we could do this automatically with keepalived, and a IAM policy that will allow the automatic detachment/re-attachment.
--UPDATE--
It looks like EBS volumes are tied to specific availability zones, so re-attaching to an instance in another AZ is impossible. The only other option I can think of is:
Create EC2 in each AZ, in public subnet (each have EIP)
Create route 53 healthcheck for TCP:2049
Create route 53 failover policies for nfs-1 (AZ1) and nfs-2 (AZ2)
The only question here is, what's the best way to keep the two NFS servers in-sync? Just cron an rsync script between them?
Or is there a best practice that I am completely missing?
There are a few options to build a highly available NFS server. Though I prefer using EFS or GlusterFS because all these solutions have their downsides.
a) DRBD
It is possible to synchronize volumes with the help of DRBD. This allows you to mirror your data. Use two EC2 instances in different availability zones for high availability. Downside: configuration and operation is complex.
b) EBS Snapshots
If a RPO of more than 30 minutes is reasonable you can use periodic EBS snapshots to be able to recover from an outage in another availability zone. This can be achieved with an Auto Scaling Group running a single EC2 instance, a user-data script and a cronjob for periodic EBS snapshots. Downside: RPO > 30 min.
c) S3 Synchronisation
It is possible to synchronize the state of an EC2 instance acting as NFS server to S3. The standby server uses S3 to stay up to date. Downside: S3 sync of lots of small files will take too long.
I recommend watching this talk from AWS re:Invent: https://youtu.be/xbuiIwEOCAs
AWS has reviewed and approved a number of SoftNAS AMIs, which are available on AWS Marketplace. The jointly published SoftNAS Architecture on AWS White Paper provides more details:
Security (pages 4-11)
HA across AZs (pages 13-14)
You can also try a 30 day free trial to see if it meets your needs.
http://softnas.com/tryaws
Full disclosure: I work for SoftNAS.
Curious if this is possible:
We have a web application that at MOST times, works just fine with our single small instance. However, when we get multiple customers running simultaneously intense queries (we are a cloud scheduling service); our instance bogs way down to near 80% cpu load and becomes pretty unresponsive.
Is there a way to have AWS fire up another small instance (or a few), quickly, only for the times that its operating under this intense load? BUT, the real question is how does this work when we have very frequent programming updates to our application? Do we have to manually create a new image everytime we upload a code change???
Thanks
You should never be running anything important on a single EC2 instance. Instances can--and do--go offline randomly. Always use an autoscaling (AS) group that spans multiple availability zones. An AS group will automatically bring new instances online when you hit a certain trigger (in your case, CPU utilization). And then it will scale down the instances when traffic subsides. Autoscaling is the heart and soul of AWS and if you're not using it, you might as well be using a cheaper (and more durable) VPS host.
No, you don't want to be creating a new AMI for each code release. Ideally you should use a base AMI (like one of Amazon's official ones) and then have it auto-provision at boot. You can use the "user data" field when you launch an AMI to bootstrap this process. It can be as simple as a bash script that pulls from your Git repo to as something as sophisticated as Puppet or Chef.
The only time I create custom AMI's is if the provisioning process just takes too long. However that can almost always be solved by storing the needed files in S3.