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HBase >> mail # user >> Acceptable CPU_WIO % ?


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Re: Acceptable CPU_WIO % ?
JM,

  Okay, I think I see what was happening.  You currently only have one
drive in the system that is showing High I/O wait correct?  You are looking
at bringing in a second drive to help distribute the load?  In your testing
with two drives you saw that RAID0 offerred superior performance vs JBOD.
 Typically when we see RAID vs JBOD we are dealing with about 6 - 12
drives.  Here are some of the pluses and minuses:

RAID0 - faster performance since the data is striped, but you are as fast
as your slowest drive and one drive failure you lose the whole volume.

JBOD - Better redundancy and faster than a RAID1, or a RAID5
configuration(unsure about a RAID4), but you are slower than RAID0

It sounds like since you only have 1 drive in the node right now, you
wouldn't be gaining or losing any redundancy by going with RAID0.  For what
it is worth, I would agree that you are I/O bound.  If you run a sar -A >
/tmp/sar.out and you take a look at the drive utilization what is your
TPS(IOPs) count that you are seeing?

On Thu, Feb 7, 2013 at 9:00 PM, Jean-Marc Spaggiari <[EMAIL PROTECTED]
> wrote:

> Hi Kevin,
>
> I'm facing some issues on one of my nodes and I'm trying to find a way
> to fix that. CPU is used about 10% by user, and 80% for WIO. So I'm
> looking for a way to improve that. The mother board can do RAIDx and
> JBOD too. It's the server I used few weeks ago to run some disks
> benchs.
>
> http://www.spaggiari.org/index.php/hbase/hard-drives-performances
>
> The conclusion was that RAID0 was 70% faster than JBOD. But JBOD was
> faster than RAID1.
>
> I have a 2TB drive in this server and was thinking about just adding
> another 2TB drive.
>
> What are the advantages of JBOD compared to RAID0? From the last tests
> I did, it was slower.
>
> Since I will have to re-format the disks anyway, I can re-run the
> tests just in case I did not configured something properly....
>
> JM
>
> 2013/2/7, Kevin O'dell <[EMAIL PROTECTED]>:
> > Hey JM,
> >
> >   Why RAID0?  That has a lot of disadvantages to using a JBOD
> > configuration?  Wait I/O is a symptom, not a problem.  Are you actually
> > experiencing a problem or are you treating for something you think should
> > be lower?
> >
> > On Thu, Feb 7, 2013 at 8:19 PM, Jean-Marc Spaggiari
> > <[EMAIL PROTECTED]
> >> wrote:
> >
> >> Hi,
> >>
> >> What is an acceptable CPU_WIO % while running an heavy MR job? Should
> >> we also try to keep that under 10%? Or it's not realistic and we will
> >> see more about 50%?
> >>
> >> One of my nodes is showing 70% :( It's WAY to much. I will add another
> >> disk tomorrow and put them in RAID0, but I'm wondering how low shoud I
> >> go?
> >>
> >> JM
> >>
> >
> >
> >
> > --
> > Kevin O'Dell
> > Customer Operations Engineer, Cloudera
> >
>

--
Kevin O'Dell
Customer Operations Engineer, Cloudera