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
Jean-Marc Spaggiari 2013-02-08, 02:50
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
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?
2013/2/8, Kevin O'dell <[EMAIL PROTECTED]>:
> 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.
> 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
> On Thu, Feb 7, 2013 at 10:23 PM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>> 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
>> > > 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
>> > > 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.
>> > > 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.
Kevin Odell 2013-02-08, 16:37
Jean-Marc Spaggiari 2013-02-09, 16:13