What is Open Stack ?
Open Stack is an open source platform that uses pooled virtual resources to build and manage private and public clouds. It handle the core cloud-computing services of compute, networking, storage, identity, and image services It offers unlimited storage pools and supports block-IO from a variety of vendors, as well as object file storage.
Open Stack Storage Option :
There are 4 storage option in Open Stack
Block Storage (cinder)
Ephemeral storage (nova)
Object Storage (swift)
Image storage (glance)
- Block Storage (cinder) :
This is most important and popular storage option in Open Stack. Block storage manually created by the users. In this storage mechanism when you delete or relaunch an instance then you can keep data in cinder block storage and re-attached into new instance.We can extend a cinder volume if need to grow the capacity of disk used by a cloud instance we can use a volume as an external hard drive and it’s attach it to an instance. we can attached a single instance at a time.
2. Ephemeral storage (nova):
An ephemeral storage is deleted when an instance is itself deleted by the cloud user or admin It is used when VM are short-lived and data does not need to persist beyond the life of a given VM . It means this is use for short period of time. In this storage size is determined by instance and image used in Open Stack.The size of ephemeral storage is determined by the flavour of the instance and the image used. It is very fast.
- Object Storage (swift)
Swift stores an object’s metadata with the object itself. We can access file by API or URL. Object storage is very suitable as low-cost storage, for example for virtual machine images, snapshots, photos, video and backups.This is ideal for static data. It is Secure, scalable and reliable online storage
4. Image Storgae (Glance):
In the above diagram when client request an image then glance-api service access storage network (br-storage) and pulls it into cache. If client again request the same image then gives directly from the cache.
It store and retrieve virtual machine disk images.Images can be used as a template in setting up a new server, usually images are stored in swift object service.