incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From aaron morton <aa...@thelastpickle.com>
Subject Re: nodetool repair -pr enough in this scenario?
Date Tue, 05 Jun 2012 18:45:10 GMT
-pr is a new feature added in 1.0. It was added for efficiency, not functionality. With -pr
repair does 1/RF the work it does without it.

> Am I understood correctly, that “repair” with or without –PR is not a “repair
selected node” process, but “synchronize data range(s) between replicas” process?
Yes. 
But if you have a node that has been down for a few hours you may want to get it's primary
range repaired quickly. 

Or as sylvain says, if you are running repair on every node in the cluster you can use -pr
to reduce the duration of the repair operation.  It would have the same effect as running
repair without -pr on every RF'th node in the cluster. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 5/06/2012, at 9:19 PM, Viktor Jevdokimov wrote:

> But in any case, repair is a two way process?
> I mean that repair without –PR on node N1 will repair N1 and N2 and N3, because N2
is a replica of N1 range and N1 is a replica of N3 range?
> And if there’re more ranges, that not belongs to N1, that ranges and nodes will not
be repaired?
>  
>  
> Am I understood correctly, that “repair” with or without –PR is not a “repair
selected node” process, but “synchronize data range(s) between replicas” process?
> Single DC scenario:
> With –PR: synchronize data for only primary data range of selected node between all
nodes for that range (max number of nodes for the range = RF).
> Without –PR: synchronize data for all data ranges of selected node (primary and replica)
between all nodes of that ranges (max number of nodes for the ranges = RF*RF). Not effective
since ranges overlaps, the same ranges will be synchronized more than once (max = RF times).
> Multiple DC with 100% data range in each DC scenario: the same, only RF = sum of RF from
all DC’s.
> Is that correct?
>  
> Finally – is this process for SSTables only, excluding memtables and hints?
>  
>  
>  
> 
> 
> Best regards / Pagarbiai
> Viktor Jevdokimov
> Senior Developer
> 
> Email: Viktor.Jevdokimov@adform.com
> Phone: +370 5 212 3063, Fax +370 5 261 0453
> J. Jasinskio 16C, LT-01112 Vilnius, Lithuania
> Follow us on Twitter: @adforminsider
> What is Adform: watch this short video
> <signature-logo29.png>
> 
> Disclaimer: The information contained in this message and attachments is intended solely
for the attention and use of the named addressee and may be confidential. If you are not the
intended recipient, you are reminded that the information remains the property of the sender.
You must not use, disclose, distribute, copy, print or rely on this e-mail. If you have received
this message in error, please contact the sender immediately and irrevocably delete this message
and any copies.
> 
> From: Sylvain Lebresne [mailto:sylvain@datastax.com] 
> Sent: Tuesday, June 05, 2012 11:02
> To: user@cassandra.apache.org
> Subject: Re: nodetool repair -pr enough in this scenario?
>  
> On Tue, Jun 5, 2012 at 8:44 AM, Viktor Jevdokimov <Viktor.Jevdokimov@adform.com>
wrote:
> Understand simple mechanics first, decide how to act later.
>  
> Without –PR there’s no difference from which host to run repair, it runs for the
whole 100% range, from start to end, the whole cluster, all nodes, at once.
>  
> That's not exactly true. A repair without -pr will repair all the ranges of the node
on which repair is ran. So it will only repair the ranges that the node is a replica for.
It will *not* repair the whole cluster (unless the replication factor is equal to the number
of nodes in the cluster but that's a degenerate case). And hence it does matter on which host
repair is run (it always matter, whether you use -pr or not).
>  
> In general you want to use repair without -pr in case where you want to repair a specific
node. Typically, if a node was dead for a reasonably long time, you may want to run a repair
(without -pr) on that specific node to have him catch up faster (faster that if you were only
relying on read-repair and hinted-handoff).
>  
> For repairing a whole cluster, as is the case for the weekly scheduled repairs in the
initial question, you want to use -rp. You *do not* want to use repair without -pr in that
case. You do not because for that task using -pr is more efficient (and to be clear, not using
-pr won't cause problems, but it does is less efficient).
>  
> --
> Sylvain
>  
>  
>  
> With –PR it runs only for a primary range of a node you are running a repair.
> Let say you have simple ring of 3 nodes with RF=2 and ranges (per node) N1=C-A, N2=A-B,
N3=B-C (node tokens are N1=A, N2=B, N3=C). No rack, no DC aware.
> So running repair with –PR on node N2 will only repair a range A-B, for which node
N2 is a primary and N3 is a backup. N2 and N3 will synchronize A-B range one with other. For
other ranges you need to run on other nodes.
>  
> Without –PR running on any node will repair all ranges, A-B, B-C, C-A. A node you run
a repair without –PR is just a repair coordinator, so no difference, which one will be next
time.
>  
>  
>  
> 
> Best regards / Pagarbiai
> Viktor Jevdokimov
> Senior Developer
>  
> Email: Viktor.Jevdokimov@adform.com
> Phone: +370 5 212 3063, Fax +370 5 261 0453
> J. Jasinskio 16C, LT-01112 Vilnius, Lithuania
> Follow us on Twitter: @adforminsider
> What is Adform: watch this short video
> <image001.png>
> 
> Disclaimer: The information contained in this message and attachments is intended solely
for the attention and use of the named addressee and may be confidential. If you are not the
intended recipient, you are reminded that the information remains the property of the sender.
You must not use, disclose, distribute, copy, print or rely on this e-mail. If you have received
this message in error, please contact the sender immediately and irrevocably delete this message
and any copies.
>  
> From: David Daeschler [mailto:david.daeschler@gmail.com] 
> Sent: Tuesday, June 05, 2012 08:59
> To: user@cassandra.apache.org
> Subject: nodetool repair -pr enough in this scenario?
>  
> Hello,
>  
> Currently I have a 4 node cassandra cluster on CentOS64. I have been running nodetool
repair (no -pr option) on a weekly schedule like:
>  
> Host1: Tue, Host2: Wed, Host3: Thu, Host4: Fri
>  
> In this scenario, if I were to add the -pr option, would this still be sufficient to
prevent forgotten deletes and properly maintain consistency?
>  
> Thank you,
> - David


Mime
View raw message