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From Sam Overton <>
Subject Re: cassandra-shuffle time to completion and required disk space
Date Mon, 29 Apr 2013 11:08:57 GMT
An alternative to running shuffle is to do a rolling
bootstrap/decommission. You would set num_tokens on the existing hosts (and
restart them) so that they split their ranges, then bootstrap in N new
hosts, then decommission the old ones.

On 28 April 2013 22:21, John Watson <> wrote:

> The amount of time/space cassandra-shuffle requires when upgrading to
> using vnodes should really be apparent in documentation (when some is made).
> Only semi-noticeable remark about the exorbitant amount of time is a
> bullet point in:
> "Shuffling will entail moving a lot of data around the cluster and so has
> the potential to consume a lot of disk and network I/O, and to take a
> considerable amount of time. For this to be an online operation, the
> shuffle will need to operate on a lower priority basis to other streaming
> operations, and should be expected to take days or weeks to complete."
> We tried running shuffle on a QA version of our cluster and 2 things were
> brought to light:
>  - Even with no reads/writes it was going to take 20 days
>  - Each machine needed enough free diskspace to potentially hold the
> entire cluster's sstables on disk
> Regards,
> John

Sam Overton
Acunu | | @acunu

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