John Dickinson me at not.mn
Wed Aug 20 01:00:45 UTC 2014

https://swiftstack.com/blog/2012/11/21/how-the-ring-works-in-openstack-swift/ is soemthing that should be able to give you a pretty complete overview of how the ring works in Swift and how data placement works.

Let me know if you have more questions after you watch that video.


On Aug 19, 2014, at 5:34 PM, Brent Troge <brenttroge2016 at gmail.com> wrote:

> Excuse this question and for lack of basic understanding. I dropped from school at 8th grade, so everything is basically self taught. Here goes.
> I am trying to figure out where each offset/partition is placed on the ring.
> So If I have 50 drives with a weight of 100 each I come up with the below part power
> part power = log2(50 * 100) = 13
> Using that I then come up with the amount of partitions.
> partitions = 2^13 =  8192
> Now here is where my ignorance comes into play. How do I use these datapoints to determine where each offset is on the ring?
> I then guess that for each offset they will have a fixed range of values that map to that partition.
> So for example, for offset 1, all object URL md5 hashes that have a decimal value of 0 through 100 will go here(i just made up the range 0 through 100, i have no idea what the range would be with respect to my given part-power, drive, etc).   
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