Jean-Marc Spaggiari 2013-02-08, 01:19
Kevin Odell 2013-02-08, 01:43
Jean-Marc Spaggiari 2013-02-08, 02:00
Kevin Odell 2013-02-08, 02:21
-Re: Acceptable CPU_WIO % ?
Jean-Marc Spaggiari 2013-02-08, 02:50
Ok. I see with RAID0 might be better for me compare to JBOD. Also, why
do we want to use RAID1 or RAID5? We already have the redundancy done
by hadoop, is it not going to add another non-required level of
Should I already think to have 3 or even 4 drives in each node?
I tried sar -A and it's only giving me 2 lines.
root@node7:/home/hbase# sar -A
Linux 3.2.0-4-amd64 (node7) 2013-02-07 _x86_64_ (4 CPU)
21:29:54 LINUX RESTART
It was not enabled, so I just enabled it and restart sysstat, but
seems that it's still not populated.
I have the diskstats plugin installed on ganglia, so I have a LOT of
disks information, but not this specific one.
My write_bytes_per_sec is pretty low. Average is 232K for the last 2
hours. But my erad_bytes_per_sec is avera 22.83M for the same period.
The graph is looking like a comb.
I just retried sar and some data is coming.. I will need to let it run
for few more minutes to get some more data ...
2013/2/7, Kevin O'dell <[EMAIL PROTECTED]>:
> 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]
>> 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
>> 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....
>> 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
Kevin Odell 2013-02-08, 02:57
Jean-Marc Spaggiari 2013-02-08, 03:15
Azuryy Yu 2013-02-08, 03:23
Kevin Odell 2013-02-08, 13:56
Jean-Marc Spaggiari 2013-02-08, 15:43
Kevin Odell 2013-02-08, 16:37
Jean-Marc Spaggiari 2013-02-09, 16:13