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
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
> 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...
> 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.
> > 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
> > Do you want to be able to lose a drive and keep the node up? If yes,
> > 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
> > 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.
> >> 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 ...
> >> JM
> >> 2013/2/7, Kevin O'dell <[EMAIL PROTECTED]>:
> >> > 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
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