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I'm moving my person webpage to an Amazon EC2 free (for now) micro instance, and want to clarify some things.

Since the micro instance does not have any "local storage", when i am installing apache, django, mysql, etc., where is it going? Does it automatically go to an EBS, is it kept in RAM, or something else? I presume the applications must have somewhere to put their files.

How exactly does EBS work? I know it's like a mountable external drive, but for example, can i install my entire web stack (mysql/apache/django) in the EBS and have it be plug-and-play to any instance?

I've been looking at BitNami Djangostack, which installs the whole stack for you on your EBS which then plugs into the instance. Is that basically what it's doing, installing the webserver, db, etc. on the EBS, or something else? Does the data live on the EBS aswell?

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Micro instances on AWS EC2 are already what's called EBS backed instances. IE even if the instance dies/terminates then your data should still be recoverable to simply start the server up again. This is very different to non-EBS backed instances where if the instance dies or is terminated the data on that instance is lost.

This is generally where EBS steps in, the non-EBS backed instance can die but the EBS volume attached to that instance will be available again to attach to a new instance and your data saved on the EBS volume will also be available again. Think of it like SAN storage in a way.

http://aws.amazon.com/ec2/

Micro Instances Instances of this family provide a small amount of consistent CPU resources and allow you to burst CPU capacity when additional cycles are available. They are well suited for lower throughput applications and web sites that consume significant compute cycles periodically.

Micro Instance 613 MB of memory, up to 2 ECUs (for short periodic bursts), EBS storage only, 32-bit or 64-bit platform

->How exactly does EBS work? I know it's like a mountable external drive, but for example, can i install my entire web stack (mysql/apache/django) in the EBS and have it be plug-and-play to any instance? Well sort of, you'd have to have all the software and everything installed in there as well or set-up and install an instance and then point config files to say all data can be found over here in this folder (or eg attached storage). But not quite as simple you can only attach a single EBS volume to a single server at any one time, however you can create a clone of an EBS instance by snap-shotting it to AWS S3 and then re-creating another EBS volume from that snapshot. Its also important to note that EBS volumes cannot move between AWS EC2 availability zones (AV) you can only attach an EBS volume to an EC2 instance if it exists within the same AV zone.

But most basic two things here, if your running micro instance they are EBS backed so if it dies you can restart and everything should be how it was before the server died. Or you can still create an EBS volume and add it to the running instance to expand your storage space.

Either way you'll want to take snap-shots to S3 every now and again as EBS can fail and in this case your backups are the only thing to help you. AWS S3 has a substantially higher percentage of reliability.

Hope it helps

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Just to clarify, does that mean that when i SSH into the Micro-Instance, the filesystem i am traversing IS the EBS? So everything i install, save, etc. is already in the EBS? Does that mean that in this case, without local storage, EBS snapshots and burning AMI images are functionally identical and can both be used to clone/backup/save the entire state of the Micro-Instance? Or does burning AMI images of an instance without local storage not make sense? –  Li Haoyi Aug 3 '11 at 20:36
    
Yes - when you login you will be on EBS. However i'm not sure about the /mnt partition of a micro instance (if one exists), I suggest you check that one. Its also very important to note the details in this thread if you want the root volume to still exist on termination of the instance. forums.aws.amazon.com/thread.jspa?messageID=218893 In this case I guess they would be yes, however the root volume being on EBS means it will contain everything written to the volume up to the point of termination or failure, but an AMI will only be to a point in time that you created the AMI. –  Mark Aug 7 '11 at 11:56
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