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

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

Copy, by Barracuda, helps you store, protect, and share all your amazing
things. Start today: www.copy.com.


----------------------------------
Copy, by Barracuda, helps you store, protect, and share all your amazing
things. Start today: www.copy.com.
 ญญ





--
www.calcmachine.com - easy online calculator.