Week 3 Flashcards
IN GFS: does master keep a persistant copy of the location of chunk servers
no
IN GFS: how does the master know where the chunk servers are?
the list is maintained via heartbeats so that the list will always be in sync with reality despite failures
In hadoop, how do you calculate the distance between 2 nodes
the sum of their distances to their closest common ancestor
what is the distance from proc1 to rack2
- It is how many hops between
Do clients cache file data
no
does the chunk server cache file data
no, chunks are stored as local files, linux already keeps frequently accessed data in memory
what is strong consistancy
avoiding all inconsistances: no matter what identical
What is update consistancy
When two people update same data at same time, without conflict handling, server will serialize them: apply one after the other
what is an ACID transaction, and is it valid for big data.
single transaction is:
Atomic
Cosistant
Isolated
Durable
NO!
CAP Theoream
Given Consistancy, Avalilablity, and Partition Tolerance, you can only get 2
what is consistancy
every read recieved the most recent write, or an error
what is availablity
every request recieved a non error response, without guarentee that it contains the most recent write
what is partition tolerance
the system continues to operate despite an arbitrarty number of messages being dropped or delayed by network between nodes
what does eventuall consistant mean>?
at any time nodes may have replication inconsistances.
if there are no more updates, eventually all nodes will be updated to the same value
What does a mutation do
changes the content or metadata of a chunk
what is this, each of these are diff chunk servers
inconsistant and defined
what is this, each of these are diff chunk servers
consistant but undefined
what is this, each of these are diff chunk servers
defined
