This blog would be third part of previous posts here and here. In this blog post I would focus on what are the use cases of using reserved capacity and advertise capacity. I have created super simple Visio below and has three examples. All nodes have same configuration. Single appliance with four nodes. Each node has two SSD and four HDD. Each node gets 10TB usable capacity when configured in cluster. Bottom one is default configuration. Here for sake of discussion we have created single storage pool and created three containers. By default each container gets 40 TB of storage. All containers are thin provisioned and space is consumed on first cum first basis.
Middle example explains reserve capacity. Three containers are created. First container I have reserved 10TB, second and third containers are created with default configuration. As result of reserved capacity, containers 2 and 3 have now only 30TB usable capacity, while container 1 has 10 TB reserved capacity. Reserved capacity can be extremely helpful in case you need to charge the customer on basis on allocation model and pay as go model. You can allocate 40 TB for customerA in container 1 and reserve 10 TB for him. You could charge customerA for upfront 10 TB and he can pay for 30 TB as and when he uses it. As storage pool is shared, there is no guarantee that storage will be available post 10 TB usage
Top example is of advertise capacity. Advertise capacity is interdependent on reserved capacity. You cannot reserve 10 TB and advertise 15 TB. Hypervizor cannot see and use anything beyond advertise capacity. In our example I have advertise only 2TB, container 1 & 2 will see 40 TB as maximum usable capacity, while container 3 will see only 2 TB maximum usable capacity. Hope this is clear now.
Let’s move to remains part of the previous blog. I would to share the mind map I have created for compression, deduplication and Erasure Coding features. I have used Edraw mindmap software. It is excellent if you wish to add style to your mindmaps.
In deduplication mindmaps it is worth to mention there two tiers where deduplication occurs I.e. Performance tiers and capacity tiers. And each tier has some requirements to meet.
In compression mindmap what compression library is used and use cases for compression.
In Erasure Coding, map explains what is made of strip and draw bags of having bigge strip size and increase you restore time. Give a special attention to prerequisites and recommendation section which I have mentioned I will share in this post.
Hope you find it useful.