Benefits of EBS vs instance-store and vice-versa

Question

I m unclear as to what benefits I get from EBS vs  instance-store for my instances on Amazon EC2  If anything  it seems that EBS is way more useful  stop  start  persist   better speed  at relatively little difference in cost     Also  is there any metric as to whether more people are using EBS now that it s available  considering it is still relatively new

User · Answer

Most people choose to use EBS backed instance as it is stateful. It is to safer because everything you have running and installed inside it, will survive stop/stop or any instance failure.

Instance store is stateless, you loose it with all the data inside in case of any instance failure situation. However, it is free and faster because the instance volume is tied to the physical server where the VM is running.

User · Answer

99  of our AWS setup is recyclable  So for me it doesn t really matter if I terminate an instance -- nothing is lost ever  E g  my application is automatically deployed on an instance from SVN  our logs are written to a central syslog server   The only benefit of instance storage that I see are cost-savings  Otherwise EBS-backed instances win  Eric mentioned all the advantages      2012-07-16  I would phrase this answer a lot different today   I haven t had any good experience with EBS-backed instances in the past year or so  The last downtimes on AWS pretty much wrecked EBS as well   I am guessing that a service like RDS uses some kind of EBS as well and that seems to work for the most part  On the instances we manage ourselves  we have got rid off EBS where possible   Getting rid to an extend where we moved a database cluster back to iron    real hardware   The only remaining piece in our infrastructure is a DB server where we stripe multiple EBS volumes into a software RAID and backup twice a day  Whatever would be lost in between backups  we can live with   EBS is a somewhat flakey technology since it s essentially a network volume  a volume attached to your server from remote  I am not negating the work done with it     it is an amazing product since essentially unlimited persistent storage is just an API call away  But it s hardly fit for scenarios where I O performance is key   And in addition to how network storage behaves  all network is shared on EC2 instances  The smaller an instance  e g  t1 micro  m1 small  the worse it gets because your network interfaces on the actual host system are shared among multiple VMs    your EC2 instance  which run on top of it   The larger instance you get  the better it gets of course  Better here means within reason   When persistence is required  I would always advice people to use something like S3 to centralize between instances  S3 is a very stable service  Then automate your instance setup to a point where you can boot a new server and it gets ready by itself  Then there is no need to have network storage which lives longer than the instance   So all in all  I see no benefit to EBS-backed instances what so ever  I rather add a minute to bootstrap  then run with a potential SPOF

User · Answer

I m just starting to use EC2 myself so not an expert  but Amazon s own documentation says      we recommend that you use the local instance store for temporary data and  for data requiring a higher level of durability  we recommend using Amazon EBS volumes or backing up the data to Amazon S3    Emphasis mine   I do more data analysis than web hosting  so persistence doesn t matter as much to me as it might for a web site  Given the distinction made by Amazon itself  I wouldn t assume that EBS is right for everyone   I ll try to remember to weigh in again after I ve used both

User · Answer

EBS is like the virtual disk of a VM     Durable  instances backed by EBS can be freely started and stopped  saving money  Can be snapshotted at any point in time  to get point-in-time backups AMIs can be created from EBS snapshots  so the EBS volume becomes a template for new systems   Instance storage is    Local  so generally faster Non-networked  in normal cases EBS I O comes at the cost of network bandwidth  except for EBS-optimized instances  which have separate EBS bandwidth  Has limited I O per second IOPS  Even provisioned I O maxes out at a few thousand IOPS Fragile   As soon as the instance is stopped  you lose everything in instance storage     Here s where to use each    Use EBS for the backing OS partition and permanent storage  DB data  critical logs  application config  Use instance storage for in-process data  noncritical logs  and transient application state  Example  external sort storage  tempfiles  etc  Instance storage can also be used for performance-critical data  when there s replication between instances  NoSQL DBs  distributed queue message systems  and DBs with replication  Use S3 for data shared between systems  input dataset and processed results  or for static data used by each system when lauched  Use AMIs for prebaked  launchable servers

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I ve had the exact same experience as Eric at my last position  Now in my new job  I m going through the same process I performed at my last job    rebuilding all their AMIs for EBS backed instances - and possibly as 32bit machines  cheaper - but can t use same AMI on 32 and 64 machines     EBS backed instances launch quickly enough that you can begin to make use of the Amazon AutoScaling API which lets you use CloudWatch metrics to trigger the launch of additional instances and register them to the ELB  Elastic Load Balancer   and also to shut them down when no longer required    This kind of dynamic autoscaling is what AWS is all about - where the real savings in IT infrastructure can come into play  It s pretty much impossible to do autoscaling right with the old s3  InstanceStore -backed instances

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For someone new to all this and if accidentally landed here  As of now all AMI s in quickstart section are EBS backed     Also there s a good explanation at official doc for difference between EBS and Instance store     amp  this image pretty much sums it up

User · Answer

The bottom line is you should almost always use EBS backed instances   Here s why   EBS backed instances can be set so that they cannot be  accidentally  terminated through the API  EBS backed instances can be stopped when you re not using them and resumed when you need them again  like pausing a Virtual PC   at least with my usage patterns saving much more money than I spend on a few dozen GB of EBS storage  EBS backed instances don t lose their instance storage when they crash  not a requirement for all users  but makes recovery much faster  You can dynamically resize EBS instance storage  You can transfer the EBS instance storage to a brand new instance  useful if the hardware at Amazon you were running on gets flaky or dies  which does happen from time to time  It is faster to launch an EBS backed instance because the image does not have to be fetched from S3  If the hardware your EBS-backed instance is scheduled for maintenance  stopping and starting the instance automatically migrates to new hardware  I was also able to move an EBS-backed instance on failed hardware by force-stopping the instance and launching it again  your mileage may vary on failed hardware     I m a heavy user of Amazon and switched all of my instances to EBS backed storage as soon as the technology came out of beta   I ve been very happy with the result   EBS can still fail - not a silver bullet  Keep in mind that any piece of cloud-based infrastructure can fail at any time   Plan your infrastructure accordingly   While EBS-backed instances provide certain level of durability compared to ephemeral storage instances  they can and do fail   Have an AMI from which you can launch new instances as needed in any availability zone  back up your important data  e g  databases   and if your budget allows it  run multiple instances of servers for load balancing and redundancy  ideally in multiple availability zones    When Not To  At some points in time  it may be cheaper to achieve faster IO on Instance Store instances  There was a time when it was certainly true  Now there are many options for EBS storage  catering to many needs  The options and their pricing evolve constantly as technology changes  If you have a significant amount of instances that are truly disposable  they don t affect your business much if they just go away   do the math on cost vs  performance  EBS-backed instances can also die at any point in time  but my practical experience is that EBS is more durable

User · Answer

Eric pretty much nailed it  We  Bitnami  are a popular provider of free AMIs for popular applications and development frameworks  PHP  Joomla  Drupal  you get the idea   I can tell you that EBS-backed AMIs are significantly more popular than S3-backed  In general I think s3-backed instances are used for distributed  time-limited jobs  for example  large scale processing of data  where if one machine fails  another one is simply spinned up  EBS-backed AMIS tend to be used for  traditional  server tasks  such as web or database servers that keep state locally and thus require the data to be available in the case of crashing    One aspect I did not see mentioned is the fact that you can take snapshots of an EBS-backed instance while running  effectively allowing you to have very cost-effective backups of your infrastructure  the snapshots are block-based and incremental

User · Answer

If you run multiple instance and assign a scheduled service of AWS Instance as one of your priority on Avoiding Unexpected Charges  I would recommend not to use the instance-store      As explained on documentation of EBS   Volumes   and the answer from j2d3 and Siddharth Sharma the   instance-store can run for as long as you want  but it cannot be   stopped  Means that the service cannot be scheduled by an Automatic   Start Stop or Instance   Recovery    Moreover  for this kind of scheme there is also no benefit to use EBS Backed on Elastic Beanstalk as it is designed to ensure that all the resources you need are keep running  It will always do an automatically relaunches any services that you stop    Reviewing all the rest  out of the total charges on using the VPC  EBS and ELB that added to EC2-Classic  the EC2-VPC with ELB is mostly the best choice where unlike on EC2-Classic  a stopped instance retains its associated Elastic IP addresses and the EBS volume is stored automatically   As conclusion  taking the main part of your question      it seems that EBS is way more useful  stop  start  persist   better   speed  at relatively little difference in cost       The answer is yes but if your instance is EBS-based  it can be stopped  It will remain in your account  you will not be charged for it  You will be charge only the volume but EBS is charged hourly  You may also consider that among all available types you have a flexibility to Resize the EBS Volume   Beside the benefits that already listed by Eric  it shall also be aware that in term of cost S3 may or may not be cheaper than EBS  I agree that it relatively little difference in cost if you keep running both types of instance within the same platform and architecture of the application all the time    However if there a scenario to run the application on a lower cost service  pull all unhandled task and role them to the VPC EBS via a pipeline or lambda within a short time basis say  lt 1 hour a day  which impossible to do when you use an instance-store  then it will be a different story

User · Answer

We like instance-store  It forces us to make our instances completely recyclable  and we can easily automate the process of building a server from scratch on a given AMI  This also means we can easily swap out AMIs  Also  EBS still has performance problems from time to time

[amazon-ec2] Benefits of EBS vs. instance-store (and vice-versa)

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