Motivation & Assumptions

PB-level Blob storage

Traditional NFS based desgin (Each image stored as a file) has metadata bottleneck: large metadata size severely limits the metadata hit ratio.

Explain more about the metadata overhead

For the Photos application most of this metadata, such as permissions, is unused and thereby wastes storage capacity. Yet the more significant cost is that the file’s metadata must be read from disk into memory in order to find the file itself. While insignificant on a small scale, multiplied over billions of photos and petabytes of data, accessing metadata is the throughput bottleneck.

Solution

Eliminates the metadata overhead by aggregating hundreds of thousands of images in a single haystack store file.

https://www.usenix.org/legacy/event/osdi10/tech/full_papers/Beaver.pdf