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From Matt Kap <matvey1...@gmail.com>
Subject Re: hinted handoff disabling trade-offs
Date Thu, 21 Mar 2013 02:34:34 GMT
Thanks Aaron, appreciate the advice.

On Tue, Mar 19, 2013 at 3:14 AM, aaron morton <aaron@thelastpickle.com> wrote:
>  I think I understand what it means for
> application-level data, but the part I'm not entirely sure about is
> what it could mean for Cassandra internals.
>
> Internally it means the write will not be retries to nodes that were either
> down or did not ack before rpc_timeout. That's all.
>
> If you are doing thing with read_repair_chance == 0 and CL ONE you are in a
> very eventually consistent world. The only thing that will guarantee
> consistency for you now is running nodetool repair.
>
>
>
>
> My cluster is under heavy write load. I'm considering disabling Hinted
> Handoffs so the nodes recover quicker in case compactions begin to
> back up.
>
> If the node cluster is approaching capacity, then ultimately the thing to do
> is add more nodes. The only things to do are disable the commit log and use
> a lower CL.
>
> If it's approaching capacity you will start to see pending mutations back
> up, maybe some dropped mutations and the maybe an increase in the difference
> between the latency reported in the proxyhistograms and the cfhistograms or
> cfstats.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 16/03/2013, at 4:50 PM, Matt Kap <matvey1414@gmail.com> wrote:
>
> Thanks Aaron.
>
> I am using CL=ONE. read_repair_chance=0. The part which I'm wondering
> about is what happens to the internal Cassandra writes if Hinted
> Handoffs are disabled. I think I understand what it means for
> application-level data, but the part I'm not entirely sure about is
> what it could mean for Cassandra internals.
>
> My cluster is under heavy write load. I'm considering disabling Hinted
> Handoffs so the nodes recover quicker in case compactions begin to
> back up.
>
> On Wed, Mar 6, 2013 at 2:06 AM, aaron morton <aaron@thelastpickle.com>
> wrote:
>
> The advantage of HH is that it reduces the probability of a DigestMismatch
> when using a CL > ONE. A DigestMismatch means the read has to run a second
> time before returning to the client.
>
> - No risk of hinted-handoffs building up
> - No risk of hinted-handoffs flooding a node that just came up
>
>
> See the yaml config settings for the max hint window and the throttling.
>
> Can anyone suggest any other factors that I'm missing here. Specifically
> reasons
> not to do this.
>
>
> If you are doing this for performance first make sure your data model is
> efficient, that you are doing the most efficient reads (see my presentation
> here http://www.datastax.com/events/cassandrasummit2012/presentations), and
> your caching is bang on. Then consider if you can tune the CL, and if your
> client is token aware so it directs traffic to a node that has it.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 4/03/2013, at 9:19 PM, Michael Kjellman <mkjellman@barracuda.com> wrote:
>
> Also, if you have enough hints being created that its significantly
> impacting your heap I have a feeling things are going to get out of sync
> very quickly.
>
> On Mar 4, 2013, at 9:17 PM, "Wz1975" <wz1975@YAHOO.COM> wrote:
>
> Why do you think disabling hinted handoff will improve memory usage?
>
>
> Thanks.
> -Wei
>
> Sent from my Samsung smartphone on AT&T
>
>
> -------- Original message --------
> Subject: Re: hinted handoff disabling trade-offs
> From: Michael Kjellman <mkjellman@barracuda.com>
> To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> CC:
>
>
> Repair is slow.
>
> On Mar 4, 2013, at 8:07 PM, "Matt Kap" <matvey1414@gmail.com> wrote:
>
> I am looking to get a second opinion about disabling hinted-handoffs. I
> have an application that can tolerate a fair amount of inconsistency
> (advertising domain), and so I'm weighting the pros and cons of hinted
> handoffs. I'm running Cassandra 1.0, looking to upgrade to 1.1 soon.
>
> Pros of disabling hinted handoffs:
> - Reduces heap
> - Improves GC performance
> - No risk of hinted-handoffs building up
> - No risk of hinted-handoffs flooding a node that just came up
>
> Cons
> - Some writes can be lost, at least until repair runs
>
> Can anyone suggest any other factors that I'm missing here. Specifically
> reasons
> not to do this.
>
> Cheers!
> -Matt
>
>
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