*The High CPU may be WAIT IOs, which would mean that you’re cpu is waiting for reads from the local disks.*
Yes I think thats what is going on but I am trying to understand why it happens only in case of snapshot MR but if I run the same job without using snapshot everything is normal. What is the difference in snapshot version which can cause such a spike ? I looking through the code for snapshot version if I can find something. cores / disks == 24 / 12 or 40 / 12. We are using 10K sata drives on our datanodes. Rahul On Wed, May 13, 2015 at 10:00 AM, Michael Segel <[email protected]> wrote: > Without knowing your exact configuration… > > The High CPU may be WAIT IOs, which would mean that you’re cpu is waiting > for reads from the local disks. > > What’s the ratio of cores (physical) to disks? > What type of disks are you using? > > That’s going to be the most likely culprit. > > On May 13, 2015, at 11:41 AM, rahul malviya <[email protected]> > wrote: > > > > Yes. > > > > On Wed, May 13, 2015 at 9:40 AM, Ted Yu <[email protected]> wrote: > > > >> Have you enabled short circuit read ? > >> > >> Cheers > >> > >> On Wed, May 13, 2015 at 9:37 AM, rahul malviya < > [email protected] > >>> > >> wrote: > >> > >>> Hi, > >>> > >>> I have recently started running MR on hbase snapshots but when the MR > is > >>> running there is pretty high CPU usage on datanodes and I start seeing > IO > >>> wait message in datanode logs and as soon I kill the MR on Snapshot > >>> everything come back to normal. > >>> > >>> What could be causing this ? > >>> > >>> I am running cdh5.2.0 distribution. > >>> > >>> Thanks, > >>> Rahul > >>> > >> > >
