Glance-Store Drivers

Glance-Store Drivers


Last week I mentioned that I had been working on migrating Glance-replicator to using the requests library. This week I have been helping out with improving the help text for Glance configuration options.

I have worked on the configuration options for some of the drivers in Glance Store till now. To begin with, it is important to understand what Glance Store is and what it does. Glance Store performs all the file operations for Glance. It handles the interactions with the local file systems as well as with the external storage back ends. Thus it is the interface between Glance and external data stores. Glance Store provides this interface with external data stores through drivers. It provides several different drivers like that for HTTP, RBD, VMware, S3, Sheepdog, File System, Cinder and Swift.

I worked on improving the help text for the configuration options for the VMware, HTTP, RBD and S3 drivers. While working on some of these driver options, I learned a few things about some of these data stores.

When I first started working on the RBD options, I didn’t really know much about what RBD is. So firstly, what is RBD? RBD stands for RADOS block device. RADOS (Reliable Autonomic Distributed Object Store) distributes objects across the storage cluster and replicates objects for fault tolerance. RBD is one of the storage systems that you can use to store and access your data when using RADOS storage. RBD facilitates storage of block-based data in the storage system. It breaks down block-based data into small chunks which are then stored as objects in RADOS. These objects are stored in virtual block-devices (thus the name RADOS block device) in the storage cluster.

Another driver that I worked with this week was the S3 store driver. Again, I didn’t really know much about the S3 storage system before I started working on its options. So again, the first question is: what is S3? S3 refers to the Amazon Simple Storage Service (Amazon S3). S3 stores the data in the form of objects within buckets. Here, object refers to a file and any metadata related to it. Thus, buckets are containers for objects in the S3 storage system.

Thats it for now. Thanks for reading! 😀


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