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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: how to know if nodetool cleanup is safe?
Date Tue, 23 Aug 2011 17:06:13 GMT
On Tue, Aug 23, 2011 at 11:56 AM, Sam Overton <soverton@acunu.com> wrote:

> On 21 August 2011 12:34, Yan Chunlu <springrider@gmail.com> wrote:
>
>> since "nodetool cleanup" could remove hinted handoff,  will it cause the
>> data loss?
>
>
> Hi Yan,
>
> Hints are not guaranteed to be delivered and "nodetool cleanup" is one of
> the reasons for that. This will only cause data-loss if you are writing at
> CL.ANY where a hint counts as a write. If you are writing at CL.ONE or above
> then at least one replica must receive the data for the write to succeed, so
> losing hints will not cause data-loss.
>
> If a hint is not delivered then the replica to which it was intended will
> become consistent after a read-repair, or after manual anti-entropy repair.
>
> Sam
>
> --
> Sam Overton
> Acunu | http://www.acunu.com | @acunu
>

If you run nodetool tpstats on each node in your cluster and ensure none of
them have an active or pending threads in the Hinted stage no hints are
currently being delivered. But as pointed out above Hinted Handoff is a best
effort system.

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