Thanks for that info.
I did see in the documentation that a value of 16 was not recommended for >50
hosts. Our existing hbase is 76 regionservers so I would imagine that
(eventually) we will see a similar figure.
There will be some scenarios where an initial setup may have (eg) 2 x 8 HDD and
future expansion adds either more HDD or newer nodes with larger storage. It
couldn’t be guaranteed that the storage would double but might increase by
either less than 2x, or 3-4 x existing amount resulting in a heterogenous
storage configuration. In these cases how would it affect efficiency if the
token figure were the same across all nodes?
From: Elliott Sims
Sent: Thursday, June 16, 2022 12:24 AM
To: user@cassandra.apache.org
Subject: Re: Configuration for new(expanding) cluster and new admins.
EXTERNAL
If you set a different num_tokens value for new hosts (the value should never
be changed on an existing host), the amount of data moved to that host will be
proportional to the num_tokens value. So, if the new hosts are set to 32 when
they're added to the cluster, those hosts will get twice as much data as the
initial 16-token hosts.
I think it's generally advised to keep a Cassandra cluster identical in terms
of hardware and num_tokens, at least within a DC. I suspect having a lot of
different values would slow down Reaper significantly, but I've had decent
results so far adding a few hosts with beefier hardware and num_tokens=32 to an
existing 16-token cluster.
On Wed, Jun 15, 2022 at 1:33 AM Marc Hoppins
mailto:marc.hopp...@eset.com>> wrote:
Hi all,
Say we have 2 datacentres with 12 nodes in each. All hardware is the same.
4-core, 2 x HDD (eg, 4TiB)
num_tokens = 16 as a start point
If a plan is to gradually increase the nodes per DC, and new hardware will have
more of everything, especially storage, I assume I increase the num_tokens
value. Should I have started with a lower value?
What would be considered as a good adjustment for:
Any increase in number of HDD for any node?
Any increase in capacity per HDD for any node?
Is there any direct correlation between new token count and the proportional
increase in either quantity of devices or total capacity, or is any adjustment
purely arbitrary just to differentiate between varied nodes?
Thanks
M
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