Tuesday, January 28, 2014

In this post, I wanted to start on a book for Splunk. I will have to defer that to the next few posts. Instead I want to add a few more items on AWS specifically Amazon EC2 instance store volumes. These are called ephemeral drives. and provide block level storage.  The blocks are preconfigured and pre-attached to the same physical server that hosts the EC2 instance. The EC2 instance determines the size of the storage. In some instances, such as micro instance there may be no instance storage and the Amazon EBS storage may be used instead.
Instances can have very fast HI1 solid state drive.  In contrast, HS1 instances are optimized for very high storage density and sequential IO.
Local instance store volumes are ideal for temporary storage of information  or that which is continually changing. such as buffers, caches, scratch data, and other temporary content, or for data that is replicated across a fleet of instances such as a load balanced pool of servers.
The instance owns the data and storage unlike EBS where store volumes can be attached or detached. High I/O typically uses instance store volumes backed by SSD and are ideally suited for many high performance database workloads such as Cassandra and MongoDB.
 Data warehouses, Hadoop storage nodes, cluster file systems involve a lot of high sequential IO.
 These are better supported by high storage instances. EC2 instance storage have same performance characteristics as Amazon EBS volumes. RAID striping is supported. The bandwidth to the disks is not limited to the network.
Unlike EBS volume data, data on instance stores are persisted only for the lifetime of the instance. For durability, the main concern here is the persistence between instance reboots. The cost of the Amazon EC2 instance includes any local instance store volumes.
Storage volumes are fixed  and defined by the instance type, so scaling the number of store volume is not an option but the overall instance and data can be instantiated multiple times to scale.
Local instance store volumes are tied to a particular Amazon EC2 instance and are fixed in number and size

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