Ted, Sorry, wrong choice of words, HBase will be unreliable. I'm referring to a situation where the session timeout is caused by a very slow quorum because, as I saw it happening before, the datanodes where pegging the disk(s) while being hammered by the region servers.
J-D On Wed, Dec 8, 2010 at 10:20 AM, Ted Dunning <[email protected]> wrote: > This is a bit misleading. ZK is always reliable regardless of disk latency. > All that happens on a busy disk is that > you get longer latency for ZK transactions. For a dedicated and > well-configured machine, you can have average > latency (including committing to disk) of about 7 ms. For a multi-purpose > busy machine, you may see latencies > of 300 ms. > > Neither case will cause unreliable operation. > > On Wed, Dec 8, 2010 at 10:14 AM, Jean-Daniel Cryans > <[email protected]>wrote: > >> Basically, ZK simply needs the lowest latency to disk and network in >> order to work reliably. It's not CPU intensive, and it's only memory >> intensive if you are using tons of znodes (HBase doesn't). >> >
