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Hadoop >> mail # user >> Re: are we able to decommission multi nodes at one time?


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Re: are we able to decommission multi nodes at one time?
It's different.
If you just want to stop DN-1 a short time, just kill the DataNode process
on DN-1. then do what you want. during this time, Namenode  cannot receive
the heart beat from DN-1, then namenode start to copy block replicates on
DN-2 to another DN, supposed DN-2.

But when you start DN-1 again, Namenode receive the DN-1 registration, then
namenode stop to copy the DN-1's block replicates even if NN doesn't finish
coping.

Am I explain clearly?

On Wed, Apr 3, 2013 at 9:43 AM, Henry Junyoung Kim <[EMAIL PROTECTED]>wrote:

> @Harsh
>
> What's the reasons to make big gaps for removing nodes between
> decommission and just down nodes?
> In my understanding, both are necessary to copy un-replicated blocks to
> another alive nodes.
> If main costs of  them are this one, total elapsed time couldn't be big
> different.
>
> Could you share some articles or documents to understand about
> decommissioning procedures?
> - explaining is always thanks ;)
>
>
> 2013. 4. 2., 오후 5:37, Harsh J <[EMAIL PROTECTED]> 작성:
>
> > Yes, you can do the downtime work in steps of 2 DNs at a time,
> > especially since you mentioned the total work would be only ~30mins at
> > most.
> >
> > On Tue, Apr 2, 2013 at 1:46 PM, Henry Junyoung Kim
> > <[EMAIL PROTECTED]> wrote:
> >> the rest of nodes to be alive has enough size to store.
> >>
> >> for this one that you've mentioned.
> >>> its easier to do so in a rolling manner without need of a
> >>> decommission.
> >>
> >> to check my understanding, just shutting down 2 of them and then 2 more
> and then 2 more without decommissions.
> >>
> >> is this correct?
> >>
> >>
> >> 2013. 4. 2., 오후 4:54, Harsh J <[EMAIL PROTECTED]> 작성:
> >>
> >>> Note though that its only possible to decommission 7 nodes at the same
> >>> time and expect it to finish iff the remaining 8 nodes have adequate
> >>> free space for the excess replicas.
> >>>
> >>> If you're just going to take them down for a short while (few mins
> >>> each), its easier to do so in a rolling manner without need of a
> >>> decommission. You can take upto two down at a time on a replication
> >>> average of 3 or 3+, and put it back in later without too much data
> >>> movement impact.
> >>>
> >>> On Tue, Apr 2, 2013 at 1:06 PM, Yanbo Liang <[EMAIL PROTECTED]>
> wrote:
> >>>> It's reasonable to decommission 7 nodes at the same time.
> >>>> But may be it also takes long time to finish it.
> >>>> Because all the replicas in these 7 nodes need to be copied to
> remaining 8
> >>>> nodes.
> >>>> The size of transfer from these nodes to the remaining nodes is equal.
> >>>>
> >>>>
> >>>> 2013/4/2 Henry Junyoung Kim <[EMAIL PROTECTED]>
> >>>>>
> >>>>> :)
> >>>>>
> >>>>> currently, I  have 15 data nodes.
> >>>>> for some tests, I am trying to decommission until 8 nodes.
> >>>>>
> >>>>> Now, the total dfs used size is 52 TB which is including all
> replicated
> >>>>> blocks.
> >>>>> from 15 to 8, total spent time is almost 4 days long. ;(
> >>>>>
> >>>>> someone mentioned that I don't need to decommission node by node.
> >>>>> for this case, is there no problems if I decommissioned 7 nodes at
> the
> >>>>> same time?
> >>>>>
> >>>>>
> >>>>> 2013. 4. 2., 오후 12:14, Azuryy Yu <[EMAIL PROTECTED]> 작성:
> >>>>>
> >>>>> I can translate it to native English: how many nodes you want to
> >>>>> decommission?
> >>>>>
> >>>>>
> >>>>> On Tue, Apr 2, 2013 at 11:01 AM, Yanbo Liang <[EMAIL PROTECTED]>
> wrote:
> >>>>>>
> >>>>>> You want to decommission how many nodes?
> >>>>>>
> >>>>>>
> >>>>>> 2013/4/2 Henry JunYoung KIM <[EMAIL PROTECTED]>
> >>>>>>>
> >>>>>>> 15 for datanodes and 3 for replication factor.
> >>>>>>>
> >>>>>>> 2013. 4. 1., 오후 3:23, varun kumar <[EMAIL PROTECTED]> 작성:
> >>>>>>>
> >>>>>>>> How many nodes do you have and replication factor for it.
> >>>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>
> >>>
> >>>
> >>>
> >>> --
> >>> Harsh J
> >>
> >
> >
> >
> > --
> > Harsh J
>
>