Thanks for the great info, Eric!
On 12/19/2012 8:59 PM, Eric Newton wrote:
> It depends on the number of drives you have, too.
> I run ingesters and scanners on every slave node, a single batchwalker
> on the master node.
> You want at least 100K for outgoing buffers for your ingester for each
> slave node you have.
> A large in-memory map is probably less useful than block index to get
> your query performance to be faster.
> Once you start getting to 5G / tablet, the number of files per tablet
> causes merging minor compactions, which cuts your performance in half.
> Increasing the number of files will reduce query performance, so that
> gives you a basic way to control ingest vs query performance.
> Pre-splitting to 20 tablets/server will give you the sweet-spot for
> ingest performance; add more if you have more drives. It allows for for
> more parallel writes during minor compactions.
> If you have more than 4 drives per node, try doubling the number of
> ingesters you run.
> I like to tweak everything until I get the system load on each machine
> to be roughly the number of real cores after 12 hours. This is hard to
> do without a spindle for every two CPUs.
> It's important to watch for failed/failing hardware. You can sample the
> outgoing write buffers of the ingesters (using netstat). If you see a
> node constantly having data queued going to it, try taking it out of the
> cluster. You can do the same for datanodes, too. At dozens of nodes,
> this is not really important. When you get to hundreds, it becomes much
> more likely that a single node will flake out after a day of abuse.
> On Wed, Dec 19, 2012 at 8:10 PM, Josh Elser <[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>> wrote:
> In playing around with the continuous ingest collection of code
> (ingest, walkers, batchwalkers, scanners and agitators), I found
> myself blindly guessing at how many of each of these processes I
> should use.
> Are there some generic thoughts as to what might be an ideal
> saturation point for N tservers?
> I initially split my hosts 4 ways and ran (N/4) of each process
> (ingest, walkers, batchwalkers, and scanners), ratcheting down the
> number of threads ingest and batchwalkers (to avoid saturating CPU
> and memory). Should I try to balance (query threads * query clients)
> + (ingest threads * ingest clients) against the available threads
> per host and adjust the BatchWriter send buffers similarly in regard
> to memory available?
> I appreciate anyone's insight.
> - Josh