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


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Jean-Marc Spaggiari 2013-02-08, 01:19
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Kevin Odell 2013-02-08, 01:43
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Jean-Marc Spaggiari 2013-02-08, 02:00
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Kevin Odell 2013-02-08, 02:21
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Jean-Marc Spaggiari 2013-02-08, 02:50
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Kevin Odell 2013-02-08, 02:57
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Jean-Marc Spaggiari 2013-02-08, 03:15
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Azuryy Yu 2013-02-08, 03:23
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Kevin Odell 2013-02-08, 13:56
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Re: Acceptable CPU_WIO % ?
Hi Kevin,

I think it will take time before I get a chance to have 5 drives in
the same server, so I will see at that time to test RAID5.

I'm going to add one drive per server today or tomorrow to try to
improve that. What IOPs should I try to have? 100? Less? It will all
be SATA3 drives and I will configure all in RAID0.

It doesn't seems to me to be an issue to lose one node, since data
will be replicated everywhere else. I will "simply" have to replace
the failing disk and restart the node, no?

JM

2013/2/8, Kevin O'dell <[EMAIL PROTECTED]>:
> Azuryy,
>
>   The main reason to recommend against RAID is that it is slow and it adds
> redundancy that we already have in Hadoop.  RAID0 is another story as long
> as all of the drives are healthy and you don't mind losing the whole volume
> if you lose one drive.
>
> JM,
>
>   I would not even waste my time testing RAID5 or RAID6(unless it is just
> for educational purposes :) ).  200+ IOPs consistently on one SATA drive is
> pretty high, that would explain your high I/O wait time.  If your use case
> allows for you to lose the whole node, there is not a good reason for you
> to shy away from RAID0.  Please let us know how this plays out with your
> environment.
>
> On Thu, Feb 7, 2013 at 10:23 PM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>
>> JM,
>>
>> I don't have the context, but if you are using Hadoop/Hbase, so don't do
>> RAID on your disk.
>>
>>
>> On Fri, Feb 8, 2013 at 11:15 AM, Jean-Marc Spaggiari <
>> [EMAIL PROTECTED]> wrote:
>>
>> > Ok. I see. For my usecase I prefer to loose the data and have faster
>> > process. So I will go for RAID0 and keep the replication factor to
>> > 3... If at some point I have 5 disks in the node, I will most probably
>> > give a try to RAID5 and see the performances compared to the other
>> > RAID/JBOD options.
>> >
>> > Is there a "rule", like, 1 HD per core? Or we can't really simplify
>> > that
>> > much?
>> >
>> > So far I have that in the sar output:
>> > 21:35:03          tps      rtps      wtps   bread/s   bwrtn/s
>> > 21:45:03       218,85    215,97      2,88  45441,95    308,04
>> > 21:55:02       209,73    206,67      3,06  43985,28    378,32
>> > 22:05:04       215,03    211,71      3,33  44831,00    312,95
>> > Average :      214,54    211,45      3,09  44753,09    333,07
>> >
>> > But I'm not sure what it means. I will wait for tomorrow to get more
>> > results, but my job will be done over night, so I'm not sure the
>> > average will be accurate...
>> >
>> > JM
>> >
>> >
>> > 2013/2/7, Kevin O'dell <[EMAIL PROTECTED]>:
>> > > JM,
>> > >
>> > >   I think you misunderstood me.  I am not advocating any form of RAID
>> for
>> > > Hadoop.  It is true that we already have redundancy built in with
>> > > HDFS.
>> >  So
>> > > unless you were going to do something silly like sacrifice speed to
>> > > run
>> > > RAID1 or RAID5 and lower your replication to 2...just don't do it :)
>> > >  Anyway, yes you probably should have 3 - 4 drives per node if not
>> more.
>> > >  At that point then the you will really see the benefit of JBOD over
>> > RAID0
>> > >
>> > > Do you want to be able to lose a drive and keep the node up?  If yes,
>> > then
>> > > JBOD is for you.  Do you not care if you lose that node due to drive
>> > > failure? You just need speed, then RAID0 may be the correct choice.
>>  Sar
>> > > will take some time to populate.  Give it about 24 hours and you
>> > > should
>> > be
>> > > able to glean some interesting information.
>> > >
>> > > On Thu, Feb 7, 2013 at 9:50 PM, Jean-Marc Spaggiari
>> > > <[EMAIL PROTECTED]
>> > >> wrote:
>> > >
>> > >> 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
>> > >> redundancy?
>> > >>
>> > >> 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.
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Kevin Odell 2013-02-08, 16:37
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Jean-Marc Spaggiari 2013-02-09, 16:13