Thanks. This is great to know.
On Mon, Jul 30, 2012 at 3:33 PM, Eric Newton <[email protected]> wrote: > Yes, the key/value pairs are replicated in redundant logs on other machines. > > We run long tests in which we ingest data and kill random servers; > this mechanism is robust up to the point to which it is configured. > That is, if you lose the right number of machines, you will not be > able to recover the in-memory data. The default number of node > failures needed to prevent recovery is 2, though this can be changed > by configuration. > > -Eric > > On Mon, Jul 30, 2012 at 3:19 PM, Edmon Begoli <[email protected]> wrote: >> What is the redundancy/recovery mechanism of Write-Ahead Log and MemTable. >> >> I am specifically asking about this statement and the parts about: >> >> "When a write arrives at a TabletServer it is written to a Write-Ahead >> Log and then inserted into a sorted data structure in memory called a >> MemTable. >> ... >> If a TabletServer fails, the Master detects it and automatically >> reassigns the tablets assigned from the failed server to other >> servers. >> Any key-value pairs that were in memory at the time the TabletServer >> are automatically reapplied from the Write-Ahead Log to prevent any >> loss of data." >> >> I.e. what happens if machine holding a MemTable crashes. Will >> key-value pairs that we in memory have been replicated already? >> >> Thank you, >> Edmon
