Given 1 trillion messages on fb and each message has at max 10 words.
How do you build the index table and how many machines do you need on the cluster to store the index table?
One possible answer
Total data = 1 trillion * 10 words * 6 bytes / word = 60TB = one small NetApp box
Index by hashed userid; will distribute traffic effectively across servers; cache active users recent messages in memory.
Cannot use Netapp box. From what I read in FB engg blog, they have all the info in main memory of server.
Total data = 1 trillion * 10 words * 6 bytes / word = 60TB + 1TB for Indexes.
Considering servers have 64 GB ram. 61 GB usable to store index, 1000 servers.
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Read 2 other posts: [Design] Distributed hash table and [Design] Cloud, Grid and Cluster.