I've launched an instance of the Basic 32-bit Amazon Linux AMI which has an 8GB volume as it's root device. If I terminate it, the EBS volume is destroyed as well. What I'd like to know is whether or not my data is protected (for example, the apache document root, or MySQL data) if the server crashes? A lot of tutorials seem to indicate that another EBS volume should be created and my data stored on that, but I'm not really seeing why two EBS volumes are needed?
Or is the current setup okay for a web server setup?
Many thanks in advance for your help!
When you spin an EC2 instance up, the root volume is ephemeral - that is, when the instance is terminated, the root volume is destroyed** (taking any data you put there with it). It doesn't matter how you partition that ephemeral volume and where you tuck your data on it - when it is destroyed, everything contained in that volume is lost.
So if the data in the volume is entirely transient and fully recoverable/retrievable from somewhere else the next time you need it, there's no problem; terminate the instance, then spin a new one up and re-acquire the data you need to carry on working.
However, if the data is NOT transient, and needs to be persisted so that work can carry on after an instance crash (and by crash, I mean something that terminates the instance or otherwise renders it inoperable and unrecoverable) then your data MUST NOT be on the root volume, but should be on another EBS volume which is attached to the instance. If and when that instance terminates or breaks irretrievably, your data is safe on that other volume - it can then be re-attached to a new instance for work to continue.
** the exception is where your instance is EBS-backed and you swapped root volumes - in this case, the root volume is left behind after the instance terminates because it wasn't part of the 'package' created by the AMI when you started it.
The other volume would be needed in case your server gets broken and you cannot start it. In such case you would just remove initial server, create a second one and attach the additional storage to the new server. You cannot attach root volume of one server to another.
Related
According to the AWS documentation "any data stored in the RAM of the host computer or the instance store volumes of the host computer is gone." Does this mean that the web application I installed on my EC2 instance will be deleted if I stop running my instance?
I apologize for the naive question. I am new to this and worried I might make a mistake.
An Amazon EC2 instance is just like a normal computer. If you turn it off, anything in RAM is lost. Also, if you reboot either computer, the contents of RAM is lost (well, more like 'forgotten', but effectively the same).
Just like your home computer, if you reboot or stop/start an EC2 instance, it boots up again. Whatever software you have installed on the computer is still there. However, applications you were running will only start if you have configured a startup script to run the app again.
Typically, when software such as a web server is installed on a computer, it is configured to automatically start again when the computer is turned on/rebooted in future.
Elastic Block Store (EBS) disk volumes act just like a disk in a normal computer. If an EC2 instance is stopped and later started again, the contents of the disk is still there, unchanged.
Bottom line: It's just like a home computer. Don't panic.
Adding to John's answer, as long as you do not use an Instance Store volume, to store your web application, you are good to go.
The data in an instance store persists only during the lifetime of its
associated instance. If an instance reboots (intentionally or
unintentionally), data in the instance store persists. However, data
in the instance store is lost under the following circumstances:
The underlying disk drive fails
The instance stops
The instance terminates
If however you are using an EBS volume, these conditions do not apply and you are free to start and stop your instance any number of times you want.
Yes unless you have EBS volume attached to EC2. If you are using an EBS-backed instance, you can stop and restart that instance without affecting the data stored in the attached volume
One of my instances was preventing me from logging so I stopped it, detached its volume, spun up a new instance, and attached the old volume. The problem is, the old volume is being treated as the root device. Because of this, I still cannot log in to the new instance (although I can do so if I don't attach the old volume).
Is there any way to fix this issue using the AWS Management Console?
It seems like you have attached your old volume in "/dev/sda1". Deattach your old volume and attach it to "/dev/sdf".
This is caused by the filesystems on each volume having the same label (the value returned by e.g. e2label /dev/xvda1). The server correctly starts booting from the first volume, and then the bootloader, there, sees the second volume having the label it anticipates for the root volume, and continues booting with the second volume as root. This an os-level setting, not visible to the AWS infrastructure.
Workaround: don't attach the second volume until after the instance has booted. EBS volumes can be attached to an instance at any time -- they don't have to be present when the instance is started. After unmount, they can also be detached at any time, with the instance still running.
To resolve this, I had to make a snapshot of the old volume first. I then created a new AMI using that snapshot. I included the old volume as an extra storage so that it's explicitly defined not to be treated as a root device.
I then created a new instance using that AMI. I was able to finally log in to the new instance. From there, I just mounted the volume.
We are working with an EC2 instance in Amazon Web Services but we have lost our .pem.
In order to create a new one, we are following this guidance:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-key-pairs.html#replacing-lost-key-pair
However, we are a bit worried because of this warning:
When you stop an instance, the data on any instance store volumes is
erased. Therefore, if you have any data on instance store volumes that
you want to keep, be sure to back it up to persistent storage.
We cannot access the instance, therefore we cannot really make a proper backup. Instead, we have make a snapshot of the volumes in Elastic Block Store.
We are wondering if this is enough and we can indeed stop the instance to proceed to the pair key recover or we need to do something else in order not to lose any data.
It depends on the type of instance.
If it's EBS backed you are probably safe to proceed as the volume will be reattached.
If it's instance store backed and you lost access to it you basically have lost what's on that machine.
By the sounds of it it's EBS backed. If it's instance store backed and you later created and attached an EBS volume and used that, you're going to be able to restore/reattach that volume just fine - but it's going to be to another machine.
Depending on how many instances we are talking about you should also be able to take an AMI Image of the running instance which will take snapshot of the EBS but also the exact state of the instance.
However if the instance's root device type is using a EBS backed store all the data should be safe so saving a snapshot and relaunching a new instance with the snapshot should have the data.
Good luck.
I thought I clearly understood the difference between instance-store and EBS backed AMIs.
But http://aws.amazon.com/maintenance-help/ says "if you are running an EBS-backed AMI, you can stop and then restart your instance in order to easily re-launch it. This will cause the loss of any data you have saved on the local instance store of the instance,"
Stop/start does NOT lose the sysvol data, so this confuses me.
I'm assuming that here, by "local instance store", they mean the backing EBS volume (the sysvol), and I'm thinking that they meant to say "terminate" instead of stop. Am I correct?
Terminating an EBS-backed instance will not cause your data to be deleted. You can still access the EBS volume until you delete it (unless you set it to delete when your instance is terminated).
Local instance store refers to hard drive space on the actual physical server that is running your instance. You can see the available instance store by doing sudo fdisk -l. Some images come with some instance store volumes already mounted (see df -h). Otherwise you'll have to mount and format the instance store volumes before you can use them.
Data on an instance store volume is lost when you stop (not terminate) your instance because it is local to a physical server, and your instance might start up on a new server.
Quite simply, EC2 is running your virtual server on some physical server. The root filesystem can either be on a local disk (ephemeral storage) or on network attached storage (EBS). With EBS, they can snapshot it for backups or to make a copy, so EBS is far more flexible, although not as fast as a local disk in the server where your instance is running.
In order to make this all work, when you shutdown an ephemeral server, amazon wipes the disk in order to reallocate it to the next customer. There is no need or reason for them to do that with EBS, since it was not physically attached to that server in the first place.
You might note, that even EBS backed instances (depending on size) come with an allocation of ephemeral storage (2-500gig+) which can be used for swap, logs, or whatever else you want to do with them. The only issue of course is that should the server be shutdown, or should there be a catastrophic disk or hardware error, you'll lose that data. You can still manually back it up, in the same way people have backed up traditional servers over the years.
Making your own AMI from an EBS backed server is trivial now, and can be done easily through the AWS web interface. Making a non-EBS backed AMI is a very complicated task the last time I tried to do it. With that said, there are certain use cases where it makes a lot of sense to consider using purely ephemeral storage. Computation or memory/cache nodes that have no need to persist data will be faster and cost less.
I am trying to stop a Amazon EC2 instance and get the warning message
Warning: Please note that any data on the ephemeral storage of your instance will be lost when it is stopped.
My Question
What data is stored in ephemeral storage of an Amazon EC2 instance?
Basically, root volume (your entire virtual system disk) is ephemeral, but only if you choose to create AMI backed by Amazon EC2 instance store.
If you choose to create AMI backed by EBS then your root volume is backed by EBS and everything you have on your root volume will be saved between reboots.
If you are not sure what type of volume you have, look under EC2->Elastic Block Store->Volumes in your AWS console and if your AMI root volume is listed there then you are safe. Also, if you go to EC2->Instances and then look under column "Root device type" of your instance and if it says "ebs", then you don't have to worry about data on your root device.
More details here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/RootDeviceStorage.html
Anything that is not stored on an EBS volume that is mounted to the instance will be lost.
For example, if you mount your EBS volume at /mystuff, then anything not in /mystuff will be lost. If you don't mount an ebs volume and save stuff on it, then I believe everything will be lost.
You can create an AMI from your current machine state, which will contain everything in your ephemeral storage. Then, when you launch a new instance based on that AMI it will contain everything as it is now.
Update: to clarify based on comments by mattgmg1990 and glenn bech:
Note that there is a difference between "stop" and "terminate". If you "stop" an instance that is backed by EBS then the information on the root volume will still be in the same state when you "start" the machine again. According to the documentation, "By default, the root device volume and the other Amazon EBS volumes attached when you launch an Amazon EBS-backed instance are automatically deleted when the instance terminates" but you can modify that via configuration.
To be clear and answer #Dean's question: EBS-type root storage doesn't seem to be ephemeral. Data is persistent across reboots and actually it doesn't make any sense to use ebs-backed root volume which is 'ephemeral'. This wouldn't be different from image-based root volume.
For EC2 instance
Stop & Start != Reboot
so for ephemeral storage (Instance Store)
Stop cause data lost
Reboot will not
According to AWS documentation [https://aws.amazon.com/premiumsupport/knowledge-center/instance-store-vs-ebs/] instance store volumes is not persistent through instance stops, terminations, or hardware failures.
Any AMI created from instance stored disk doesn't contain data present in instance store so all instances launched by this AMI will not have data stored in instance store. Instance store can be used as cache for applications running on instance, for all persistent data you should use EBS.
ephemeral is just another name of root volume when you launch Instance from AMI backed from Amazon EC2 instance store
So Everything will be stored on ephemeral.
if you have launched your instance from AMI backed by EBS volume then your instance does not have ephemeral.
refer: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html#instance-store-volumes
The data in an instance store persists only during the lifetime of
its associated instance. If an instance reboots (intentionally or
unintentionally), data in the instance store persists. However,
data in the instance store is lost under any of the following
circumstances:
- The underlying disk drive fails
- The instance stops
- The instance hibernates
- The instance terminates